diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index f614c903c8837c..4a9a64e5577989 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -715,6 +715,9 @@ def _use_posix_spawn():
         # os.posix_spawn() is not available
         return False
 
+    if ((_env := os.environ.get('_PYTHON_SUBPROCESS_USE_POSIX_SPAWN')) in ('0', '1')):
+        return bool(int(_env))
+
     if sys.platform in ('darwin', 'sunos5'):
         # posix_spawn() is a syscall on both macOS and Solaris,
         # and properly reports errors
diff --git a/Misc/NEWS.d/next/Library/2025-04-06-19-25-12.gh-issue-129204.sAVFO6.rst b/Misc/NEWS.d/next/Library/2025-04-06-19-25-12.gh-issue-129204.sAVFO6.rst
new file mode 100644
index 00000000000000..d8994bf760b7bc
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-04-06-19-25-12.gh-issue-129204.sAVFO6.rst
@@ -0,0 +1,2 @@
+Introduce new ``_PYTHON_SUBPROCESS_USE_POSIX_SPAWN`` environment variable knob in
+:mod:`subprocess` to control the use of :func:`os.posix_spawn`.