diff --git a/Misc/NEWS.d/next/Windows/2025-05-20-12-35-33.gh-issue-118234.HjbkIh.rst b/Misc/NEWS.d/next/Windows/2025-05-20-12-35-33.gh-issue-118234.HjbkIh.rst
new file mode 100644
index 00000000000000..a1b1ef84db8d93
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2025-05-20-12-35-33.gh-issue-118234.HjbkIh.rst
@@ -0,0 +1,2 @@
+Avoid socket failure with missing SYSTEMROOT env var on Windows. Patch by
+John Keith Hohm.
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index 92c9aa8b510dca..c4877dd790aa72 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -403,6 +403,21 @@ remove_unusable_flags(PyObject *m)
     return 0;
 }
 
+/* issue #118234, avoid WinError 10106 with empty environment */
+static void ensure_system_root() {
+    LPCWSTR name = L"SystemRoot";
+    DWORD size = GetEnvironmentVariableW(name, NULL, 0);
+    if (size) {
+        return;
+    }
+    wchar_t root[4096];
+    UINT len = GetWindowsDirectoryW(root, 4096);
+    if (len == 0 || len >= 4096) {
+        return;
+    }
+    SetEnvironmentVariableW(name, root);
+}
+
 #endif
 
 #include <stddef.h>
@@ -5618,6 +5633,10 @@ sock_initobj_impl(PySocketSockObject *self, int family, int type, int proto,
     SOCKET_T fd = INVALID_SOCKET;
     socket_state *state = find_module_state_by_def(Py_TYPE(self));
 
+#ifdef MS_WINDOWS
+    ensure_system_root();
+#endif
+
 #ifndef MS_WINDOWS
 #ifdef SOCK_CLOEXEC
     int *atomic_flag_works = &sock_cloexec_works;