diff --git a/backends/xnnpack/CMakeLists.txt b/backends/xnnpack/CMakeLists.txt
index 002d351155d..bc2bfc5fe61 100644
--- a/backends/xnnpack/CMakeLists.txt
+++ b/backends/xnnpack/CMakeLists.txt
@@ -73,6 +73,20 @@ foreach(fbs_file ${_xnnpack_schema__srcs})
 endforeach()
 
 # Generate the headers from the .fbs files.
+
+if (WIN32)
+add_custom_command(
+  OUTPUT ${_xnnpack_schema__outputs}
+  COMMAND
+    ${FLATC_EXECUTABLE} --cpp --cpp-std c++11 --scoped-enums -o
+    "${_xnnpack_schema__include_dir}/executorch/backends/xnnpack/serialization"
+    ${_xnnpack_schema__srcs}
+  COMMAND powershell -Command "Move-Item -Path ${_xnnpack_flatbuffer__outputs} -Destination ${_xnnpack_schema__outputs}"
+  WORKING_DIRECTORY ${EXECUTORCH_ROOT}
+  COMMENT "Generating xnnpack_schema headers"
+  VERBATIM
+)
+else()
 add_custom_command(
   OUTPUT ${_xnnpack_schema__outputs}
   COMMAND
@@ -84,6 +98,7 @@ add_custom_command(
   COMMENT "Generating xnnpack_schema headers"
   VERBATIM
 )
+endif()
 
 add_library(xnnpack_schema INTERFACE ${_xnnpack_schema__outputs})
 set_target_properties(xnnpack_schema PROPERTIES LINKER_LANGUAGE CXX)
diff --git a/build/resolve_buck.py b/build/resolve_buck.py
index d70fe94b415..804ab22a033 100644
--- a/build/resolve_buck.py
+++ b/build/resolve_buck.py
@@ -11,7 +11,6 @@
 import platform
 import stat
 import sys
-import tempfile
 import urllib.request
 
 from dataclasses import dataclass
@@ -85,6 +84,12 @@ class BuckInfo:
         archive_name="buck2-x86_64-apple-darwin.zst",
         target_versions=["3eb1ae97ea963086866b4d2d9ffa966d"],
     ),
+    ("windows", "x86_64"): BuckInfo(
+        archive_name="buck2-x86_64-pc-windows-msvc.exe.zst",
+        target_versions=[
+            "bf1685c4c4ddd9de4592b5a955cb7326fd01e6c4d5f561643422bed961a17401"
+        ],
+    ),
 }
 
 
@@ -135,6 +140,8 @@ def resolve_buck2(args: argparse.Namespace) -> Union[str, int]:
         os_family = "linux"
     elif sys.platform.startswith("darwin"):
         os_family = "darwin"
+    elif sys.platform.startswith("win"):
+        os_family = "windows"
 
     platform_key = (os_family, arch)
     if platform_key not in BUCK_PLATFORM_MAP:
@@ -193,12 +200,12 @@ def resolve_buck2(args: argparse.Namespace) -> Union[str, int]:
 
             buck2_archive_url = f"https://github.com/facebook/buck2/releases/download/{target_buck_version}/{buck_info.archive_name}"
 
-            with tempfile.NamedTemporaryFile() as archive_file:
+            try:
                 print(f"Downloading buck2 from {buck2_archive_url}...", file=sys.stderr)
-                urllib.request.urlretrieve(buck2_archive_url, archive_file.name)
+                archive_file, _ = urllib.request.urlretrieve(buck2_archive_url)
 
                 # Extract and chmod.
-                with open(archive_file.name, "rb") as f:
+                with open(archive_file, "rb") as f:
                     data = f.read()
                     decompressed_bytes = zstd.decompress(data)
 
@@ -207,6 +214,8 @@ def resolve_buck2(args: argparse.Namespace) -> Union[str, int]:
 
                 file_stat = os.stat(buck2_local_path)
                 os.chmod(buck2_local_path, file_stat.st_mode | stat.S_IEXEC)
+            finally:
+                os.remove(archive_file)
 
             return buck2_local_path
 
diff --git a/devtools/CMakeLists.txt b/devtools/CMakeLists.txt
index 776d421a8d3..144995803c3 100644
--- a/devtools/CMakeLists.txt
+++ b/devtools/CMakeLists.txt
@@ -157,19 +157,45 @@ file(MAKE_DIRECTORY
      ${_program_schema__include_dir}/executorch/devtools/bundled_program
 )
 
+# Note that the flatcc project actually writes its outputs into the source
+# tree instead of under the binary directory, and there's no way to change
+# that behavior.
+if(WIN32)
+  set(_flatcc_bin_path ${_flatcc_source_dir}/bin/${CMAKE_BUILD_TYPE}/flatcc)
+else()
+  set(_flatcc_bin_path ${_flatcc_source_dir}/bin/flatcc)
+endif()
+
+if(WIN32)
+  add_custom_command(
+    OUTPUT ${_etdump_schema__outputs}
+    COMMAND
+      # Note that the flatcc project actually writes its outputs into the source
+      # tree instead of under the binary directory, and there's no way to change
+      # that behavior.
+      ${_flatcc_bin_path} -cwr -o
+      ${_program_schema__include_dir}/executorch/devtools/etdump
+      ${_etdump_schema__srcs}
+    # COMMAND powershell -Command "Remove-Item -Path " ${_etdump_schema_cleanup_paths} " -Force -ErrorAction SilentlyContinue"
+    COMMAND powershell -Command "if (" "'${_etdump_schema_cleanup_paths}'" "-ne '') { Remove-Item -Path " "'${_etdump_schema_cleanup_paths}'" " -Force -ErrorAction SilentlyContinue }"
+    DEPENDS ${_etdump_schema_gen_dep}
+    COMMENT "Generating etdump headers"
+  )
+else()
 add_custom_command(
   OUTPUT ${_etdump_schema__outputs}
   COMMAND
     # Note that the flatcc project actually writes its outputs into the source
     # tree instead of under the binary directory, and there's no way to change
     # that behavior.
-    ${_flatcc_source_dir}/bin/flatcc -cwr -o
+    ${_flatcc_bin_path} -cwr -o
     ${_program_schema__include_dir}/executorch/devtools/etdump
     ${_etdump_schema__srcs}
   COMMAND rm -f ${_etdump_schema_cleanup_paths}
   DEPENDS ${_etdump_schema_gen_dep}
   COMMENT "Generating etdump headers"
 )
+endif()
 
 add_library(
   etdump ${CMAKE_CURRENT_SOURCE_DIR}/etdump/etdump_flatcc.cpp
diff --git a/examples/models/llama/CMakeLists.txt b/examples/models/llama/CMakeLists.txt
index 6a4aee11d22..7097f3e9c15 100644
--- a/examples/models/llama/CMakeLists.txt
+++ b/examples/models/llama/CMakeLists.txt
@@ -80,7 +80,7 @@ find_package(gflags REQUIRED)
 # find `executorch` libraries Same as for gflags
 set(executorch_DIR ${CMAKE_CURRENT_BINARY_DIR}/../../../lib/cmake/ExecuTorch)
 find_package(executorch CONFIG REQUIRED)
-if(CMAKE_TOOLCHAIN_IOS OR ANDROID)
+if(CMAKE_TOOLCHAIN_IOS OR ANDROID OR WIN32 OR APPLE)
   target_link_options_shared_lib(executorch)
 endif()
 
@@ -98,6 +98,13 @@ add_subdirectory(runner)
 set(link_libraries gflags)
 set(_srcs main.cpp)
 
+# in Windows, cpublas and extension_threadpool have duplicated symbols
+if(WIN32 AND TARGET xnnpack_backend)
+  set(CPUBLAS "")
+else()
+  set(CPUBLAS "cpublas")
+endif()
+
 if(EXECUTORCH_BUILD_KERNELS_OPTIMIZED)
   list(
     APPEND
@@ -105,7 +112,7 @@ if(EXECUTORCH_BUILD_KERNELS_OPTIMIZED)
     optimized_native_cpu_ops_lib
     optimized_kernels
     portable_kernels
-    cpublas
+    ${CPUBLAS}
     eigen_blas
   )
   target_link_options_shared_lib(optimized_native_cpu_ops_lib)
@@ -131,10 +138,18 @@ if(EXECUTORCH_BUILD_TORCHAO)
 endif()
 
 set(XNNPACK_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/../../../backends/xnnpack)
+
+# in Windows, xnnpack_backend and extension_threadpool have duplicated symbols
+if(WIN32 AND TARGET xnnpack_backend)
+  set(EXTENSION_THREADPOOL "")
+else()
+  set(EXTENSION_THREADPOOL "extension_threadpool")
+endif()
+
 # Extra compile option and include dir for pthreadpool
 if(EXECUTORCH_BUILD_PTHREADPOOL)
   list(APPEND _common_compile_options -DET_USE_THREADPOOL)
-  list(APPEND link_libraries extension_threadpool pthreadpool)
+  list(APPEND link_libraries ${EXTENSION_THREADPOOL} pthreadpool)
   list(APPEND _common_include_directories
        ${XNNPACK_ROOT}/third-party/pthreadpool/include
   )
@@ -142,7 +157,7 @@ endif()
 
 # Extra sources for cpuinfo
 if(EXECUTORCH_BUILD_CPUINFO)
-  list(APPEND link_libraries extension_threadpool cpuinfo)
+  list(APPEND link_libraries ${EXTENSION_THREADPOOL} cpuinfo)
   list(APPEND _common_include_directories
        ${XNNPACK_ROOT}/third-party/cpuinfo/include
   )
@@ -216,9 +231,6 @@ target_include_directories(llama_main PUBLIC ${_common_include_directories})
 target_link_libraries(llama_main PUBLIC llama_runner ${link_libraries})
 target_compile_options(llama_main PUBLIC ${_common_compile_options})
 
-if(APPLE)
-  target_link_options_shared_lib(executorch)
-endif()
 
 # Print all summary
 executorch_print_configuration_summary()
diff --git a/examples/models/llama/install_requirements.bat b/examples/models/llama/install_requirements.bat
new file mode 100644
index 00000000000..e084a2191f8
--- /dev/null
+++ b/examples/models/llama/install_requirements.bat
@@ -0,0 +1,16 @@
+rem Install snakeviz for cProfile flamegraph
+rem Install sentencepiece for llama tokenizer
+pip install snakeviz sentencepiece
+
+rem Install torchao.
+pip install "%~dp0/../../../third-party/ao"
+
+rem Install lm-eval for Model Evaluation with lm-evalution-harness
+rem Install tiktoken for tokenizer
+pip install lm_eval==0.4.5
+pip install tiktoken blobfile
+rem Restore numpy if >= 2.0
+pip install "numpy<2.0"
+
+rem Call the install helper for further setup
+python examples/models/llama/install_requirement_helper.py
diff --git a/examples/models/llama/runner/CMakeLists.txt b/examples/models/llama/runner/CMakeLists.txt
index 79fcd267af0..f1e563dc5b3 100644
--- a/examples/models/llama/runner/CMakeLists.txt
+++ b/examples/models/llama/runner/CMakeLists.txt
@@ -36,6 +36,11 @@ include(${EXECUTORCH_SRCS_FILE})
 
 # build llama_runner library
 list(TRANSFORM _llama_runner__srcs PREPEND "${EXECUTORCH_ROOT}/")
+if (WIN32)
+  set_property(TARGET extension_module PROPERTY
+              IMPORTED_IMPLIB "${EXECUTORCH_ROOT}/cmake-out/lib/extension_module.lib")
+
+endif()
 
 target_include_directories(
   extension_module INTERFACE ${_common_include_directories}
@@ -52,6 +57,7 @@ list(APPEND _llama_runner__srcs
 if(CMAKE_TOOLCHAIN_IOS
    OR ANDROID
    OR APPLE
+   OR WIN32
 )
   # Building a share library on iOS requires code signing On Android we see
   # duplicated registration when using shared lib
@@ -84,4 +90,4 @@ target_link_libraries(llama_runner PUBLIC ${llama_runner_deps})
 target_include_directories(
   llama_runner INTERFACE ${_common_include_directories} ${EXECUTORCH_ROOT}
 )
-target_compile_options(llama_runner PUBLIC ${_preprocessor_flag})
+target_compile_options(llama_runner PUBLIC ${_preprocessor_flag})
\ No newline at end of file
diff --git a/extension/data_loader/file_data_loader.cpp b/extension/data_loader/file_data_loader.cpp
index 1d097cfd989..3a3f663b90b 100644
--- a/extension/data_loader/file_data_loader.cpp
+++ b/extension/data_loader/file_data_loader.cpp
@@ -14,10 +14,10 @@
 #include <cstring>
 #include <limits>
 
+#include <executorch/runtime/platform/unistd.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <unistd.h>
 
 #include <executorch/runtime/core/error.h>
 #include <executorch/runtime/core/result.h>
@@ -71,6 +71,9 @@ FileDataLoader::~FileDataLoader() {
   std::free(const_cast<char*>(file_name_));
   // fd_ can be -1 if this instance was moved from, but closing a negative fd is
   // safe (though it will return an error).
+  if (fd_ == -1) {
+    return;
+  }
   ::close(fd_);
 }
 
diff --git a/extension/data_loader/mman.h b/extension/data_loader/mman.h
new file mode 100644
index 00000000000..e03c0a86fb6
--- /dev/null
+++ b/extension/data_loader/mman.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// This file ensures that mman.h compatible functions are defined in the global
+// namespace for windows and posix environments.
+
+#pragma once
+
+#include <executorch/runtime/platform/compiler.h>
+
+#ifndef _WIN32
+
+#include <sys/mman.h>
+#include <unistd.h>
+
+ET_INLINE long get_os_page_size(){return sysconf(_SC_PAGESIZE);}
+
+#else
+
+#define NOMINMAX
+#include <windows.h>
+#undef NOMINMAX
+#include <io.h>
+
+#include <executorch/extension/data_loader/mman_windows.h>
+
+ET_INLINE long get_os_page_size() {
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  long pagesize = si.dwAllocationGranularity > si.dwPageSize
+      ? si.dwAllocationGranularity
+      : si.dwPageSize;
+  return pagesize;
+}
+
+#endif
diff --git a/extension/data_loader/mman_windows.cpp b/extension/data_loader/mman_windows.cpp
new file mode 100644
index 00000000000..d5f4f136e22
--- /dev/null
+++ b/extension/data_loader/mman_windows.cpp
@@ -0,0 +1,251 @@
+/*
+ * Copyright (c) Google Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the MIT license.
+ */
+
+/*
+ * Adapted from: https://code.google.com/archive/p/mman-win32/
+ *
+ * mman-win32
+ * mman library for Windows
+ *
+ * A light implementation of the mmap functions for MinGW.
+ *
+ * The mmap-win32 library implements a wrapper for mmap functions around the
+ * memory mapping Windows API.
+ */
+
+#include <errno.h>
+#include <io.h>
+#include <windows.h>
+
+#include "mman_windows.h"
+
+#ifndef STATUS_SECTION_TOO_BIG
+#define STATUS_SECTION_TOO_BIG ((NTSTATUS)0xC0000040L)
+#endif
+
+#ifndef FILE_MAP_EXECUTE
+#define FILE_MAP_EXECUTE 0x0020
+#endif /* FILE_MAP_EXECUTE */
+
+#define RETURN_IF_FAILED(hr) \
+  do {                       \
+    if (FAILED((hr))) {      \
+      return hr;             \
+    }                        \
+  } while (false)
+
+namespace {
+
+HRESULT try_grow_process_memory_working_set(DWORD dwSizeRequired) {
+  // Get current working set
+  size_t minWorkingSetInitial;
+  size_t maxWorkingSet;
+  if (!GetProcessWorkingSetSize(
+          GetCurrentProcess(), &minWorkingSetInitial, &maxWorkingSet)) {
+    return GetLastError();
+  }
+
+  // Calculate new sizes
+  size_t minWorkingSet = minWorkingSetInitial + dwSizeRequired;
+  if (minWorkingSet < minWorkingSetInitial) {
+    return HRESULT_FROM_WIN32(ERROR_ARITHMETIC_OVERFLOW);
+  }
+
+  if (maxWorkingSet < minWorkingSet) {
+    maxWorkingSet = minWorkingSet;
+  }
+
+  // Grow working set
+  if (!SetProcessWorkingSetSize(
+          GetCurrentProcess(), minWorkingSet, maxWorkingSet)) {
+    return GetLastError();
+  }
+  return S_OK;
+}
+
+HRESULT virtual_lock(void* pMem, DWORD dwSize) {
+  if (!VirtualLock(pMem, dwSize)) {
+    return GetLastError();
+  }
+  return S_OK;
+}
+
+HRESULT virtual_lock_allowing_working_set_growth(void* pMem, DWORD dwSize) {
+  HRESULT hr = virtual_lock(pMem, dwSize);
+
+  if (hr == HRESULT_FROM_WIN32(STATUS_SECTION_TOO_BIG)) {
+    // Attempt to grow the process working set and try again
+    RETURN_IF_FAILED(try_grow_process_memory_working_set(dwSize));
+    RETURN_IF_FAILED(virtual_lock(pMem, dwSize));
+  }
+
+  return hr;
+}
+
+static int __map_mman_error(const DWORD err, const int deferr) {
+  if (err == 0) {
+    return 0;
+  }
+  // TODO: implement
+  return err;
+}
+
+static DWORD __map_mmap_prot_page(const int prot) {
+  DWORD protect = 0;
+
+  if (prot == PROT_NONE) {
+    return protect;
+  }
+  if ((prot & PROT_EXEC) != 0) {
+    protect =
+        ((prot & PROT_WRITE) != 0) ? PAGE_EXECUTE_READWRITE : PAGE_EXECUTE_READ;
+  } else {
+    protect = ((prot & PROT_WRITE) != 0) ? PAGE_READWRITE : PAGE_READONLY;
+  }
+  return protect;
+}
+
+static DWORD __map_mmap_prot_file(const int prot) {
+  DWORD desiredAccess = 0;
+
+  if (prot == PROT_NONE) {
+    return desiredAccess;
+  }
+  if ((prot & PROT_READ) != 0) {
+    desiredAccess |= FILE_MAP_READ;
+  }
+  if ((prot & PROT_WRITE) != 0) {
+    desiredAccess |= FILE_MAP_WRITE;
+  }
+  if ((prot & PROT_EXEC) != 0) {
+    desiredAccess |= FILE_MAP_EXECUTE;
+  }
+  return desiredAccess;
+}
+
+} // namespace
+
+void* mmap(void* addr, size_t len, int prot, int flags, int fildes, off_t off) {
+  HANDLE fm, h;
+
+  void* map = MAP_FAILED;
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4293)
+#endif
+
+  const DWORD dwFileOffsetLow = (sizeof(off_t) <= sizeof(DWORD))
+      ? (DWORD)off
+      : (DWORD)(off & 0xFFFFFFFFL);
+  const DWORD dwFileOffsetHigh = (sizeof(off_t) <= sizeof(DWORD))
+      ? (DWORD)0
+      : (DWORD)((off >> 32) & 0xFFFFFFFFL);
+  const DWORD protect = __map_mmap_prot_page(prot);
+  const DWORD desiredAccess = __map_mmap_prot_file(prot);
+
+  const off_t maxSize = off + (off_t)len;
+
+  const DWORD dwMaxSizeLow = (sizeof(off_t) <= sizeof(DWORD))
+      ? (DWORD)maxSize
+      : (DWORD)(maxSize & 0xFFFFFFFFL);
+  const DWORD dwMaxSizeHigh = (sizeof(off_t) <= sizeof(DWORD))
+      ? (DWORD)0
+      : (DWORD)((maxSize >> 32) & 0xFFFFFFFFL);
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+  errno = 0;
+
+  if (len == 0
+      /* Unsupported flag combinations */
+      || (flags & MAP_FIXED) != 0
+      /* Usupported protection combinations */
+      || prot == PROT_EXEC) {
+    errno = EINVAL;
+    return MAP_FAILED;
+  }
+
+  h = ((flags & MAP_ANONYMOUS) == 0) ? (HANDLE)_get_osfhandle(fildes)
+                                     : INVALID_HANDLE_VALUE;
+
+  if ((flags & MAP_ANONYMOUS) == 0 && h == INVALID_HANDLE_VALUE) {
+    errno = EBADF;
+    return MAP_FAILED;
+  }
+
+  fm = CreateFileMapping(h, NULL, protect, dwMaxSizeHigh, dwMaxSizeLow, NULL);
+
+  if (fm == NULL) {
+    errno = __map_mman_error(GetLastError(), EPERM);
+    return MAP_FAILED;
+  }
+
+  map =
+      MapViewOfFile(fm, desiredAccess, dwFileOffsetHigh, dwFileOffsetLow, len);
+
+  CloseHandle(fm);
+
+  if (map == NULL) {
+    errno = __map_mman_error(GetLastError(), EPERM);
+    return MAP_FAILED;
+  }
+
+  return map;
+}
+
+int munmap(void* addr, size_t len) {
+  if (UnmapViewOfFile(addr))
+    return 0;
+
+  errno = __map_mman_error(GetLastError(), EPERM);
+
+  return -1;
+}
+
+int mprotect(void* addr, size_t len, int prot) {
+  DWORD newProtect = __map_mmap_prot_page(prot);
+  DWORD oldProtect = 0;
+
+  if (VirtualProtect(addr, len, newProtect, &oldProtect))
+    return 0;
+
+  errno = __map_mman_error(GetLastError(), EPERM);
+
+  return -1;
+}
+
+int msync(void* addr, size_t len, int flags) {
+  if (FlushViewOfFile(addr, len))
+    return 0;
+
+  errno = __map_mman_error(GetLastError(), EPERM);
+
+  return -1;
+}
+
+int mlock(const void* addr, size_t len) {
+  HRESULT hr = virtual_lock_allowing_working_set_growth((LPVOID)addr, len);
+  if (SUCCEEDED(hr)) {
+    return 0;
+  }
+
+  errno = __map_mman_error(hr, EPERM);
+
+  return -1;
+}
+
+int munlock(const void* addr, size_t len) {
+  if (VirtualUnlock((LPVOID)addr, len))
+    return 0;
+
+  errno = __map_mman_error(GetLastError(), EPERM);
+
+  return -1;
+}
diff --git a/extension/data_loader/mman_windows.h b/extension/data_loader/mman_windows.h
new file mode 100644
index 00000000000..4c247cd4fca
--- /dev/null
+++ b/extension/data_loader/mman_windows.h
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) Google Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the MIT license.
+ */
+
+/*
+ * Adapted from: https://code.google.com/archive/p/mman-win32/
+ *
+ * mman-win32
+ * mman library for Windows
+ *
+ * A light implementation of the mmap functions for MinGW.
+ *
+ * The mmap-win32 library implements a wrapper for mmap functions around the
+ * memory mapping Windows API.
+ */
+
+#ifndef _SYS_MMAN_H_
+#define _SYS_MMAN_H_
+
+#ifndef _WIN32_WINNT // Allow use of features specific to Windows XP or later.
+#define _WIN32_WINNT \
+  0x0501 // Change this to the appropriate value to target other versions of
+         // Windows.
+#endif
+
+/* All the headers include this file. */
+#ifndef _MSC_VER
+#include <_mingw.h>
+#endif
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define PROT_NONE 0
+#define PROT_READ 1
+#define PROT_WRITE 2
+#define PROT_EXEC 4
+
+#define MAP_FILE 0
+#define MAP_SHARED 1
+#define MAP_PRIVATE 2
+#define MAP_TYPE 0xf
+#define MAP_FIXED 0x10
+#define MAP_ANONYMOUS 0x20
+#define MAP_ANON MAP_ANONYMOUS
+
+#define MAP_FAILED ((void*)-1)
+
+/* Flags for msync. */
+#define MS_ASYNC 1
+#define MS_SYNC 2
+#define MS_INVALIDATE 4
+
+void* mmap(void* addr, size_t len, int prot, int flags, int fildes, off_t off);
+int munmap(void* addr, size_t len);
+int mprotect(void* addr, size_t len, int prot);
+int msync(void* addr, size_t len, int flags);
+int mlock(const void* addr, size_t len);
+int munlock(const void* addr, size_t len);
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif /*  _SYS_MMAN_H_ */
diff --git a/extension/data_loader/mmap_data_loader.cpp b/extension/data_loader/mmap_data_loader.cpp
index ebe74f95266..d18b7b1a98e 100644
--- a/extension/data_loader/mmap_data_loader.cpp
+++ b/extension/data_loader/mmap_data_loader.cpp
@@ -6,6 +6,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+#include <executorch/extension/data_loader/mman.h>
 #include <executorch/extension/data_loader/mmap_data_loader.h>
 
 #include <cerrno>
@@ -13,10 +14,8 @@
 #include <limits>
 
 #include <fcntl.h>
-#include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <unistd.h>
 
 #include <executorch/runtime/core/error.h>
 #include <executorch/runtime/core/result.h>
@@ -63,14 +62,16 @@ MmapDataLoader::~MmapDataLoader() {
   std::free(const_cast<char*>(file_name_));
   // fd_ can be -1 if this instance was moved from, but closing a negative fd is
   // safe (though it will return an error).
-  ::close(fd_);
+  if (fd_ != -1) {
+    ::close(fd_);
+  }
 }
 
 Result<MmapDataLoader> MmapDataLoader::from(
     const char* file_name,
     MmapDataLoader::MlockConfig mlock_config) {
   // Cache the page size.
-  long page_size = sysconf(_SC_PAGESIZE);
+  long page_size = get_os_page_size();
   if (page_size < 0) {
     ET_LOG(Error, "Could not get page size: %s (%d)", ::strerror(errno), errno);
     return Error::AccessFailed;
@@ -182,12 +183,24 @@ Result<FreeableBuffer> MmapDataLoader::load(
   Range range =
       get_overlapping_pages(static_cast<uintptr_t>(offset), size, page_size_);
 
+  size_t map_size = range.size;
+  #ifdef _WIN32
+    // On Windows, don't mmap-in memory past end of on-disk file.
+    //
+    // The Windows implementation of mmap uses CreateFileMapping which returns
+    // error STATUS_SECTION_TOO_BIG (0xc0000040) if we try to map past the end
+    // of the last page of a file mapped in as read-only.
+    if (range.start + range.size > file_size_) {
+      map_size = file_size_ - range.start;
+    }
+  #endif
+
   // Map the pages read-only. MAP_PRIVATE vs. MAP_SHARED doesn't matter since
   // the data is read-only, but use PRIVATE just to further avoid accidentally
   // modifying the file.
   void* pages = ::mmap(
       nullptr,
-      range.size,
+      map_size,
       PROT_READ,
       MAP_PRIVATE,
       fd_,
diff --git a/extension/data_loader/targets.bzl b/extension/data_loader/targets.bzl
index fcc7cba5419..1a2b77cfaeb 100644
--- a/extension/data_loader/targets.bzl
+++ b/extension/data_loader/targets.bzl
@@ -69,7 +69,16 @@ def define_common_targets():
 
     runtime.cxx_library(
         name = "mmap_data_loader",
-        srcs = ["mmap_data_loader.cpp"],
+        srcs = [
+            "mmap_data_loader.cpp",
+            "mman_windows.cpp"
+        ] if host_info().os.is_windows else [
+            "mmap_data_loader.cpp"
+        ],
+        headers = [
+            "mman.h",
+            "mman_windows.h"
+        ],
         exported_headers = ["mmap_data_loader.h"],
         visibility = [
             "//executorch/test/...",
diff --git a/extension/data_loader/test/mmap_data_loader_test.cpp b/extension/data_loader/test/mmap_data_loader_test.cpp
index a76121109a8..b217705c618 100644
--- a/extension/data_loader/test/mmap_data_loader_test.cpp
+++ b/extension/data_loader/test/mmap_data_loader_test.cpp
@@ -6,12 +6,11 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+#include <executorch/extension/data_loader/mman.h>
 #include <executorch/extension/data_loader/mmap_data_loader.h>
 
 #include <cstring>
 
-#include <unistd.h>
-
 #include <gtest/gtest.h>
 
 #include <executorch/extension/testing_util/temp_file.h>
@@ -34,7 +33,7 @@ class MmapDataLoaderTest : public ::testing::Test {
     executorch::runtime::runtime_init();
 
     // Get the page size and ensure it's a power of 2.
-    long page_size = sysconf(_SC_PAGESIZE);
+    long page_size = get_os_page_size();
     ASSERT_GT(page_size, 0);
     ASSERT_EQ(page_size & ~(page_size - 1), page_size);
     page_size_ = page_size;
diff --git a/extension/llm/custom_ops/sdpa_with_kv_cache.py b/extension/llm/custom_ops/sdpa_with_kv_cache.py
index 85021266b59..8041e25d406 100644
--- a/extension/llm/custom_ops/sdpa_with_kv_cache.py
+++ b/extension/llm/custom_ops/sdpa_with_kv_cache.py
@@ -10,6 +10,7 @@
 
 # pyre-unsafe
 
+import os
 import logging
 from pathlib import Path
 
@@ -24,7 +25,11 @@
     op2 = torch.ops.llama.fast_hadamard_transform.default
     assert op2 is not None
 except:
-    libs = list(Path(__file__).parent.resolve().glob("libcustom_ops_aot_lib.*"))
+    lib_name_pattern = "libcustom_ops_aot_lib.*"
+    if os.name == "nt":
+        lib_name_pattern = "custom_ops_aot_lib.*"
+
+    libs = list(Path(__file__).parent.resolve().glob(lib_name_pattern))
     assert len(libs) == 1, f"Expected 1 library but got {len(libs)}"
     logging.info(f"Loading custom ops library: {libs[0]}")
     torch.ops.load_library(libs[0])
diff --git a/extension/llm/runner/util.h b/extension/llm/runner/util.h
index 04d4eccc4a7..6f4954d6e0d 100644
--- a/extension/llm/runner/util.h
+++ b/extension/llm/runner/util.h
@@ -44,7 +44,7 @@ ET_EXPERIMENTAL void inline safe_printf(const char* piece) {
 ET_EXPERIMENTAL long inline time_in_ms() {
   // return time in milliseconds, for benchmarking the model speed
   struct timespec time;
-  clock_gettime(CLOCK_REALTIME, &time);
+  timespec_get(&time, TIME_UTC);
   return time.tv_sec * 1000 + time.tv_nsec / 1000000;
 }
 
diff --git a/extension/module/CMakeLists.txt b/extension/module/CMakeLists.txt
index 7d6c2485eed..6680f36cb35 100644
--- a/extension/module/CMakeLists.txt
+++ b/extension/module/CMakeLists.txt
@@ -20,6 +20,7 @@ list(TRANSFORM _extension_module__srcs PREPEND "${EXECUTORCH_ROOT}/")
 if(CMAKE_TOOLCHAIN_IOS
    OR CMAKE_TOOLCHAIN_ANDROID
    OR APPLE
+   OR WIN32
 )
   # Building a share library on iOS requires code signing On Android we see
   # duplicated registration when using shared lib
diff --git a/install_requirements.bat b/install_requirements.bat
index 4cfe4b21c4b..74ec74ab2cb 100644
--- a/install_requirements.bat
+++ b/install_requirements.bat
@@ -7,14 +7,8 @@ rem This batch file provides a basic functionality similar to the bash script.
 
 cd /d "%~dp0"
 
-rem Find the names of the python tools to use (replace with your actual python installation)
-if "%PYTHON_EXECUTABLE%"=="" (
-  if "%CONDA_DEFAULT_ENV%"=="" OR "%CONDA_DEFAULT_ENV%"=="base" OR NOT EXIST "python" (
-    set PYTHON_EXECUTABLE=python3
-  ) else (
-    set PYTHON_EXECUTABLE=python
-  )
-)
+rem Under windows it's always python
+set PYTHON_EXECUTABLE=python
 
 "%PYTHON_EXECUTABLE%" install_requirements.py %*
 
diff --git a/kernels/quantized/CMakeLists.txt b/kernels/quantized/CMakeLists.txt
index 9d2b14d8eb0..18ac299e742 100644
--- a/kernels/quantized/CMakeLists.txt
+++ b/kernels/quantized/CMakeLists.txt
@@ -112,7 +112,7 @@ if(NOT CMAKE_GENERATOR STREQUAL "Xcode"
         quantized_pybind_kernels_lib DEPS portable_lib
       )
       target_link_libraries(
-        quantized_ops_aot_lib PUBLIC quantized_ops_pybind_lib
+        quantized_ops_aot_lib PUBLIC quantized_ops_pybind_lib PUBLIC executorch_core PUBLIC portable_kernels
       )
 
       # pip wheels will need to be able to find the dependent libraries. On
diff --git a/runtime/platform/compiler.h b/runtime/platform/compiler.h
index bc07470387a..16b08d23fae 100644
--- a/runtime/platform/compiler.h
+++ b/runtime/platform/compiler.h
@@ -99,15 +99,8 @@
 
 #endif // (__cplusplus) >= 202002L
 
-/// Define a C symbol with weak linkage.
-#ifdef _MSC_VER
-// There currently doesn't seem to be a great way to do this in Windows and
-// given that weak linkage is not really critical on Windows, we'll just leave
-// it as a stub.
-#define ET_WEAK
-#else
+// Building on Windows also need this.
 #define ET_WEAK __attribute__((weak))
-#endif
 
 /**
  * Annotation marking a function as printf-like, providing compiler support
diff --git a/runtime/platform/targets.bzl b/runtime/platform/targets.bzl
index 42bb851e2cf..0c94c70c06b 100644
--- a/runtime/platform/targets.bzl
+++ b/runtime/platform/targets.bzl
@@ -68,6 +68,7 @@ def define_common_targets():
             "log.h",
             "profiler.h",
             "runtime.h",
+            "unistd.h",
         ],
         srcs = [
             "abort.cpp",
diff --git a/runtime/platform/unistd.h b/runtime/platform/unistd.h
new file mode 100644
index 00000000000..c8bc4866702
--- /dev/null
+++ b/runtime/platform/unistd.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @file
+ * unistd.h related macros for POSIX/Windows compatibility.
+ */
+#pragma once
+
+#if defined(_WIN32) && !defined(_WIN64)
+#error \
+    "You're trying to build ExecuTorch with a too old version of Windows. We need Windows 64-bit."
+#endif
+
+#if !defined(_WIN64)
+#include <unistd.h>
+#else
+#include <io.h>
+#define O_RDONLY _O_RDONLY
+#define open _open
+#define close _close
+#define read _read
+#define write _write
+#define stat _stat64
+#define fstat _fstat64
+#define off_t _off_t
+#define lseek _lseeki64
+
+#include <executorch/runtime/platform/compiler.h> // For ssize_t.
+#include <windows.h>
+// To avoid conflicts with std::numeric_limits<int32_t>::max() in
+// file_data_loader.cpp.
+#undef max
+
+inline ssize_t pread(int fd, void* buf, size_t nbytes, size_t offset) {
+  OVERLAPPED overlapped; /* The offset for ReadFile. */
+  memset(&overlapped, 0, sizeof(overlapped));
+  overlapped.Offset = offset;
+  overlapped.OffsetHigh = offset >> 32;
+
+  BOOL result; /* The result of ReadFile. */
+  DWORD bytes_read; /* The number of bytes read. */
+  HANDLE file = (HANDLE)_get_osfhandle(fd);
+
+  result = ReadFile(file, buf, nbytes, &bytes_read, &overlapped);
+  DWORD error = GetLastError();
+  if (!result) {
+    if (error == ERROR_IO_PENDING) {
+      result = GetOverlappedResult(file, &overlapped, &bytes_read, TRUE);
+      if (!result) {
+        error = GetLastError();
+      }
+    }
+  }
+  if (!result) {
+    // Translate error into errno.
+    switch (error) {
+      case ERROR_HANDLE_EOF:
+        errno = 0;
+        break;
+      default:
+        errno = EIO;
+        break;
+    }
+    return -1;
+  }
+  return bytes_read;
+}
+
+#endif // !defined(_WIN64)
\ No newline at end of file
diff --git a/setup.py b/setup.py
index ff1afa89bd6..f457ac99e8e 100644
--- a/setup.py
+++ b/setup.py
@@ -225,7 +225,7 @@ def src_path(self, installer: "InstallerBuildExt") -> Path:
             self.src = self.src.replace("%BUILD_TYPE%", cfg)
         else:
             # Remove %BUILD_TYPE% from the path.
-            self.src = self.src.replace("/%BUILD_TYPE%", "")
+            self.src = self.src.replace("%BUILD_TYPE%/", "")
 
         # Construct the full source path, resolving globs. If there are no glob
         # pattern characters, this will just ensure that the source file exists.
@@ -263,7 +263,7 @@ def __init__(
                 output is in a subdirectory named after the build type. For single-
                 config generators (like Makefile Generators or Ninja), this placeholder
                 will be removed.
-            src_name: The name of the file to install
+            src_name: The name of the file to install.
             dst: The path to install to, relative to the root of the pip
                 package. If dst ends in "/", it is treated as a directory.
                 Otherwise it is treated as a filename.
@@ -305,13 +305,17 @@ def dst_path(self, installer: "InstallerBuildExt") -> Path:
 class BuiltExtension(_BaseExtension):
     """An extension that installs a python extension that was built by cmake."""
 
-    def __init__(self, src: str, modpath: str):
+    def __init__(self, src_dir: str, src_name: str, modpath: str):
         """Initializes a BuiltExtension.
 
         Args:
-            src: The path to the file to install (typically a shared library),
-                relative to the cmake-out directory. May be an fnmatch-style
-                glob that matches exactly one file. If the path ends in `.so`,
+            src_dir: The directory of the file to install, relative to the cmake-out
+                directory. A placeholder %BUILD_TYPE% will be replaced with the build
+                type for multi-config generators (like Visual Studio) where the build
+                output is in a subdirectory named after the build type. For single-
+                config generators (like Makefile Generators or Ninja), this placeholder
+                will be removed.
+            src_name: The name of the file to install. If the path ends in `.so`,
                 this class will also look for similarly-named `.dylib` files.
             modpath: The dotted path of the python module that maps to the
                 extension.
@@ -319,6 +323,7 @@ def __init__(self, src: str, modpath: str):
         assert (
             "/" not in modpath
         ), f"modpath must be a dotted python module path: saw '{modpath}'"
+        src = os.path.join(src_dir, src_name)
         # This is a real extension, so use the modpath as the name.
         super().__init__(src=src, dst=modpath, name=modpath)
 
@@ -658,7 +663,9 @@ def get_ext_modules() -> List[Extension]:
             # portable kernels, and a selection of backends. This lets users
             # load and execute .pte files from python.
             BuiltExtension(
-                "_portable_lib.*", "executorch.extension.pybindings._portable_lib"
+                src_dir="%BUILD_TYPE%/",
+                src_name="_portable_lib.cp*",
+                modpath="executorch.extension.pybindings._portable_lib",
             )
         )
     if ShouldBuild.llama_custom_ops():