diff --git a/crypto/CMakeLists.txt b/crypto/CMakeLists.txt
index bc30702..12d15a8 100644
--- a/crypto/CMakeLists.txt
+++ b/crypto/CMakeLists.txt
@@ -204,6 +204,7 @@
   rc4/rc4.c
   refcount_c11.c
   refcount_lock.c
+  refcount_win.c
   rsa_extra/rsa_asn1.c
   rsa_extra/rsa_crypt.c
   rsa_extra/rsa_print.c
diff --git a/crypto/internal.h b/crypto/internal.h
index a4cd929..adcd444 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -548,6 +548,14 @@
 #define OPENSSL_C11_ATOMIC
 #endif
 
+// Older MSVC does not support C11 atomics, so we fallback to the Windows APIs.
+// This can be removed once we can rely on
+// https://devblogs.microsoft.com/cppblog/c11-atomics-in-visual-studio-2022-version-17-5-preview-2/
+#if !defined(OPENSSL_C11_ATOMIC) && defined(OPENSSL_THREADS) && \
+    defined(OPENSSL_WINDOWS)
+#define OPENSSL_WINDOWS_ATOMIC
+#endif
+
 // CRYPTO_REFCOUNT_MAX is the value at which the reference count saturates.
 #define CRYPTO_REFCOUNT_MAX 0xffffffff
 
diff --git a/crypto/refcount_lock.c b/crypto/refcount_lock.c
index 173267e..7886bf8 100644
--- a/crypto/refcount_lock.c
+++ b/crypto/refcount_lock.c
@@ -18,7 +18,7 @@
 #include <stdlib.h>
 
 
-#if !defined(OPENSSL_C11_ATOMIC)
+#if !defined(OPENSSL_C11_ATOMIC) && !defined(OPENSSL_WINDOWS_ATOMIC)
 
 static_assert((CRYPTO_refcount_t)-1 == CRYPTO_REFCOUNT_MAX,
               "CRYPTO_REFCOUNT_MAX is incorrect");
@@ -49,4 +49,4 @@
   return ret;
 }
 
-#endif  // OPENSSL_C11_ATOMIC
+#endif  // !OPENSSL_C11_ATOMIC && !OPENSSL_WINDOWS_ATOMICS
diff --git a/crypto/refcount_win.c b/crypto/refcount_win.c
new file mode 100644
index 0000000..7a2740b
--- /dev/null
+++ b/crypto/refcount_win.c
@@ -0,0 +1,89 @@
+/* Copyright (c) 2023, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include "internal.h"
+
+#if defined(OPENSSL_WINDOWS_ATOMIC)
+
+#include <windows.h>
+
+
+// See comment above the typedef of CRYPTO_refcount_t about these tests.
+static_assert(alignof(CRYPTO_refcount_t) == alignof(LONG),
+              "CRYPTO_refcount_t does not match LONG alignment");
+static_assert(sizeof(CRYPTO_refcount_t) == sizeof(LONG),
+              "CRYPTO_refcount_t does not match LONG size");
+
+static_assert((CRYPTO_refcount_t)-1 == CRYPTO_REFCOUNT_MAX,
+              "CRYPTO_REFCOUNT_MAX is incorrect");
+
+static uint32_t atomic_load_u32(volatile LONG *ptr) {
+  // This is not ideal because it still writes to a cacheline. MSVC is not able
+  // to optimize this to a true atomic read, and Windows does not provide an
+  // InterlockedLoad function.
+  //
+  // The Windows documentation [1] does say "Simple reads and writes to
+  // properly-aligned 32-bit variables are atomic operations", but this is not
+  // phrased in terms of the C11 and C++11 memory models, and indeed a read or
+  // write seems to produce slightly different code on MSVC than a sequentially
+  // consistent std::atomic::load in C++. Moreover, it is unclear if non-MSVC
+  // compilers on Windows provide the same guarantees. Thus we avoid relying on
+  // this and instead still use an interlocked function. This is still
+  // preferable a global mutex, and eventually this code will be replaced by
+  // [2]. Additionally, on clang-cl, we'll use the |OPENSSL_C11_ATOMIC| path.
+  //
+  // [1] https://learn.microsoft.com/en-us/windows/win32/sync/interlocked-variable-access
+  // [2] https://devblogs.microsoft.com/cppblog/c11-atomics-in-visual-studio-2022-version-17-5-preview-2/
+  return (uint32_t)InterlockedCompareExchange(ptr, 0, 0);
+}
+
+static int atomic_compare_exchange_u32(volatile LONG *ptr, uint32_t *expected32,
+                                       uint32_t desired) {
+  LONG expected = (LONG)*expected32;
+  LONG actual = InterlockedCompareExchange(ptr, (LONG)desired, expected);
+  *expected32 = (uint32_t)actual;
+  return actual == expected;
+}
+
+void CRYPTO_refcount_inc(CRYPTO_refcount_t *in_count) {
+  volatile LONG *count = (volatile LONG *)in_count;
+  uint32_t expected = atomic_load_u32(count);
+
+  while (expected != CRYPTO_REFCOUNT_MAX) {
+    const uint32_t new_value = expected + 1;
+    if (atomic_compare_exchange_u32(count, &expected, new_value)) {
+      break;
+    }
+  }
+}
+
+int CRYPTO_refcount_dec_and_test_zero(CRYPTO_refcount_t *in_count) {
+  volatile LONG *count = (volatile LONG *)in_count;
+  uint32_t expected = atomic_load_u32(count);
+
+  for (;;) {
+    if (expected == 0) {
+      abort();
+    } else if (expected == CRYPTO_REFCOUNT_MAX) {
+      return 0;
+    } else {
+      const uint32_t new_value = expected - 1;
+      if (atomic_compare_exchange_u32(count, &expected, new_value)) {
+        return new_value == 0;
+      }
+    }
+  }
+}
+
+#endif  // OPENSSL_WINDOWS_ATOMIC