diff --git a/.github/workflows/cibuildwheel.yml b/.github/workflows/cibuildwheel.yml
index a8419b9..66051f9 100644
--- a/.github/workflows/cibuildwheel.yml
+++ b/.github/workflows/cibuildwheel.yml
@@ -19,7 +19,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.21.3
+        uses: pypa/cibuildwheel@v2.23.3
         env:
           CIBW_SOME_OPTION: value
         with:
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index b73968c..dab68d1 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -24,7 +24,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python_version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.13t"]
         exclude:
           # The 3.9/3.10 arm64 Python binaries that `setup-python` tries to use
           # don't work on macOS 15 anymore, so skip those.
diff --git a/README.md b/README.md
index 9e21837..13cdd09 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,12 @@ pip install -U pip setuptools wheel
 pip install cymem
 ```
 
+### Free threading
+
+`cymem` has support for being built and run under free-threaded CPython.
+Currently `Pool` is not thread safe when used from multiple threads at once;
+**please avoid sharing a single** `Pool` instance between threads.
+
 ## Example Use Case: An array of structs
 
 Let's say we want a sequence of sparse matrices. We need fast access, and a
@@ -160,7 +166,7 @@ cdef class MatrixArray:
         self.length = len(py_matrices)
         self.matrices = <SparseMatrix**>self.mem.alloc(self.length, sizeof(SparseMatrix*))
         for i, py_matrix in enumerate(py_matrices):
-            self.matrices[i] = sparse_matrix_init(self.mem, py_matrix)
+            self.matrices[i] = sparse_matrix_init_cymem(self.mem, py_matrix)
 
 cdef SparseMatrix* sparse_matrix_init_cymem(Pool mem, list py_matrix) except NULL:
     sm = <SparseMatrix*>mem.alloc(1, sizeof(SparseMatrix))
diff --git a/pyproject.toml b/pyproject.toml
index ab36d78..f4f0898 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,9 +7,9 @@ build-backend = "setuptools.build_meta"
 
 [tool.cibuildwheel]
 build = "*"
-skip = "pp* cp36* cp37* cp38*"
+skip = "pp* cp36* cp37* cp38* *t*_i686"
 test-skip = ""
-free-threaded-support = false
+enable = ["cpython-freethreading"]
 
 archs = ["native"]
 
diff --git a/setup.py b/setup.py
index df40294..8a7b87e 100755
--- a/setup.py
+++ b/setup.py
@@ -8,11 +8,17 @@
 from setuptools.command.build_ext import build_ext
 from sysconfig import get_path
 from Cython.Build import cythonize
+from Cython.Compiler.Version import version as cython_version
+from packaging.version import Version
 
 
 PACKAGES = find_packages()
 MOD_NAMES = ["cymem.cymem"]
 
+compiler_directives = dict()
+
+if Version(cython_version) >= Version("3.1.0"):
+    compiler_directives["freethreading_compatible"] =  True
 
 # By subclassing build_extensions we have the actual compiler that will be used which is really known only after finalize_options
 # http://stackoverflow.com/questions/724664/python-distutils-how-to-get-a-compiler-that-is-going-to-be-used
@@ -100,7 +106,8 @@ def setup_package():
             version=about["__version__"],
             url=about["__uri__"],
             license=about["__license__"],
-            ext_modules=cythonize(ext_modules, language_level=2),
+            ext_modules=cythonize(ext_modules, language_level=3,
+                                  compiler_directives=compiler_directives),
             setup_requires=["cython>=0.25"],
             classifiers=[
                 "Environment :: Console",