diff --git a/BUILD.generated.bzl b/BUILD.generated.bzl
index 64bf19981..58df08c8b 100644
--- a/BUILD.generated.bzl
+++ b/BUILD.generated.bzl
@@ -415,7 +415,8 @@ crypto_sources = [
     "src/crypto/rand_extra/windows.c",
     "src/crypto/rc4/rc4.c",
     "src/crypto/refcount_c11.c",
-    "src/crypto/refcount_lock.c",
+    "src/crypto/refcount_no_threads.c",
+    "src/crypto/refcount_win.c",
     "src/crypto/rsa_extra/rsa_asn1.c",
     "src/crypto/rsa_extra/rsa_crypt.c",
     "src/crypto/rsa_extra/rsa_print.c",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 89e60bdb6..e83dc9983 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -408,7 +408,8 @@ add_library(
   src/crypto/rand_extra/windows.c
   src/crypto/rc4/rc4.c
   src/crypto/refcount_c11.c
-  src/crypto/refcount_lock.c
+  src/crypto/refcount_no_threads.c
+  src/crypto/refcount_win.c
   src/crypto/rsa_extra/rsa_asn1.c
   src/crypto/rsa_extra/rsa_crypt.c
   src/crypto/rsa_extra/rsa_print.c
diff --git a/sources.json b/sources.json
index cbb3654af..b0e3caf99 100644
--- a/sources.json
+++ b/sources.json
@@ -144,7 +144,8 @@
     "src/crypto/rand_extra/windows.c", 
     "src/crypto/rc4/rc4.c", 
     "src/crypto/refcount_c11.c", 
-    "src/crypto/refcount_lock.c", 
+    "src/crypto/refcount_no_threads.c", 
+    "src/crypto/refcount_win.c", 
     "src/crypto/rsa_extra/rsa_asn1.c", 
     "src/crypto/rsa_extra/rsa_crypt.c", 
     "src/crypto/rsa_extra/rsa_print.c", 
diff --git a/src/crypto/CMakeLists.txt b/src/crypto/CMakeLists.txt
index bc307023c..c427b20c5 100644
--- a/src/crypto/CMakeLists.txt
+++ b/src/crypto/CMakeLists.txt
@@ -203,7 +203,8 @@ add_library(
   rand_extra/windows.c
   rc4/rc4.c
   refcount_c11.c
-  refcount_lock.c
+  refcount_no_threads.c
+  refcount_win.c
   rsa_extra/rsa_asn1.c
   rsa_extra/rsa_crypt.c
   rsa_extra/rsa_print.c
diff --git a/src/crypto/internal.h b/src/crypto/internal.h
index a4cd92912..5c0473596 100644
--- a/src/crypto/internal.h
+++ b/src/crypto/internal.h
@@ -548,6 +548,24 @@ OPENSSL_EXPORT void CRYPTO_once(CRYPTO_once_t *once, void (*init)(void));
 #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
+
+// Require some atomics implementation. Contact BoringSSL maintainers if you
+// have a platform with fails this check.
+//
+// Note this check can only be done in C. From C++, we don't know whether the
+// corresponding C mode would support C11 atomics.
+#if !defined(__cplusplus) && defined(OPENSSL_THREADS) && \
+    !defined(OPENSSL_C11_ATOMIC) && !defined(OPENSSL_WINDOWS_ATOMIC)
+#error "Thread-compatible configurations require atomics"
+#endif
+
 // CRYPTO_REFCOUNT_MAX is the value at which the reference count saturates.
 #define CRYPTO_REFCOUNT_MAX 0xffffffff
 
diff --git a/src/crypto/refcount_lock.c b/src/crypto/refcount_no_threads.c
similarity index 75%
rename from src/crypto/refcount_lock.c
rename to src/crypto/refcount_no_threads.c
index 173267e38..096b4fa93 100644
--- a/src/crypto/refcount_lock.c
+++ b/src/crypto/refcount_no_threads.c
@@ -18,35 +18,25 @@
 #include <stdlib.h>
 
 
-#if !defined(OPENSSL_C11_ATOMIC)
+#if !defined(OPENSSL_THREADS)
 
 static_assert((CRYPTO_refcount_t)-1 == CRYPTO_REFCOUNT_MAX,
               "CRYPTO_REFCOUNT_MAX is incorrect");
 
-static struct CRYPTO_STATIC_MUTEX g_refcount_lock = CRYPTO_STATIC_MUTEX_INIT;
-
 void CRYPTO_refcount_inc(CRYPTO_refcount_t *count) {
-  CRYPTO_STATIC_MUTEX_lock_write(&g_refcount_lock);
   if (*count < CRYPTO_REFCOUNT_MAX) {
     (*count)++;
   }
-  CRYPTO_STATIC_MUTEX_unlock_write(&g_refcount_lock);
 }
 
 int CRYPTO_refcount_dec_and_test_zero(CRYPTO_refcount_t *count) {
-  int ret;
-
-  CRYPTO_STATIC_MUTEX_lock_write(&g_refcount_lock);
   if (*count == 0) {
     abort();
   }
   if (*count < CRYPTO_REFCOUNT_MAX) {
     (*count)--;
   }
-  ret = (*count == 0);
-  CRYPTO_STATIC_MUTEX_unlock_write(&g_refcount_lock);
-
-  return ret;
+  return *count == 0;
 }
 
-#endif  // OPENSSL_C11_ATOMIC
+#endif  // !OPENSSL_THREADS
diff --git a/src/crypto/refcount_win.c b/src/crypto/refcount_win.c
new file mode 100644
index 000000000..7a2740bc2
--- /dev/null
+++ b/src/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