diff --git a/build/build.rs b/build/build.rs
index 3f5ca4b355..fa6cdacdea 100644
--- a/build/build.rs
+++ b/build/build.rs
@@ -187,7 +187,7 @@ const ASM_TARGETS: &[AsmTarget] = &[
         perlasm_format: WIN32N,
     },
     AsmTarget {
-        oss: &[WINDOWS],
+        oss: &[WINDOWS, CYGWIN],
         arch: X86_64,
         perlasm_format: NASM,
     },
@@ -253,6 +253,7 @@ const NASM: &str = "nasm";
 const APPLE_ABI: &[&str] = &["ios", "macos", "tvos", "visionos", "watchos"];
 
 const WINDOWS: &str = "windows";
+const CYGWIN: &str = "cygwin";
 
 pub fn generate_sources_and_preassemble<'a>(
     tools: &Tools,
@@ -344,7 +345,7 @@ pub fn build_c_code(
                 // them.
                 if extension == "S"
                     && (target.arch == X86_64 || target.arch == X86)
-                    && target.os == WINDOWS
+                    && (target.os == WINDOWS || target.os == CYGWIN)
                 {
                     return false;
                 }
diff --git a/src/ec/curve25519/ops.rs b/src/ec/curve25519/ops.rs
index 969550fb00..f6dc98fdec 100644
--- a/src/ec/curve25519/ops.rs
+++ b/src/ec/curve25519/ops.rs
@@ -71,7 +71,7 @@ pub struct P3 {
 impl P3 {
     // Returns the result of multiplying the base point by the scalar in constant time.
     pub(super) fn from_scalarmult_base(scalar: &Scalar, cpu: cpu::Features) -> Self {
-        #[cfg(all(target_arch = "x86_64", not(windows)))]
+        #[cfg(all(target_arch = "x86_64", not(windows), not(target_os = "cygwin")))]
         if let Some(cpu) = super::adx::get_features(cpu) {
             return super::adx::scalarmult_base(scalar, cpu);
         }
diff --git a/src/ec/curve25519/x25519.rs b/src/ec/curve25519/x25519.rs
index 96ac71f73c..ee82d86de6 100644
--- a/src/ec/curve25519/x25519.rs
+++ b/src/ec/curve25519/x25519.rs
@@ -119,7 +119,7 @@ fn x25519_ecdh(
             return x25519_neon(out, scalar, point, cpu);
         }
 
-        #[cfg(all(target_arch = "x86_64", not(windows)))]
+        #[cfg(all(target_arch = "x86_64", not(windows), not(target_os = "cygwin")))]
         if super::adx::get_features(cpu).is_some() {
             prefixed_extern! {
                 unsafe fn x25519_scalar_mult_adx(
diff --git a/src/rand.rs b/src/rand.rs
index d9c54cabd6..07b02e2cd9 100644
--- a/src/rand.rs
+++ b/src/rand.rs
@@ -128,6 +128,7 @@ impl SystemRandom {
     all(feature = "less-safe-getrandom-espidf", target_os = "espidf"),
     target_os = "aix",
     target_os = "android",
+    target_os = "cygwin",
     target_os = "dragonfly",
     target_os = "freebsd",
     target_os = "fuchsia",