diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 20ca0d1c..f3b7fce3 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -83,6 +83,7 @@ jobs:
           - sparcv9-sun-solaris
           - x86_64-apple-darwin
           - x86_64-apple-ios
+          - x86_64-pc-cygwin
           - x86_64-pc-solaris
           # Fails with:
           # `rror calling dlltool 'x86_64-w64-mingw32-dlltool': No such file or
diff --git a/src/lib.rs b/src/lib.rs
index 4d39b05d..6f8a4a4b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -516,6 +516,7 @@ impl TcpKeepalive {
         target_os = "tvos",
         target_os = "watchos",
         target_os = "windows",
+        target_os = "cygwin",
     ))]
     pub const fn with_interval(self, interval: Duration) -> Self {
         Self {
@@ -543,6 +544,7 @@ impl TcpKeepalive {
             target_os = "netbsd",
             target_os = "tvos",
             target_os = "watchos",
+            target_os = "cygwin",
         )
     ))]
     pub const fn with_retries(self, retries: u32) -> Self {
diff --git a/src/socket.rs b/src/socket.rs
index 7f2a1edf..b6e92f54 100644
--- a/src/socket.rs
+++ b/src/socket.rs
@@ -200,6 +200,9 @@ impl Socket {
     /// non-blocking mode before calling this function), socket option can't be
     /// set *while connecting*. This will cause errors on Windows. Socket
     /// options can be safely set before and after connecting the socket.
+    ///
+    /// On Cygwin, a Unix domain socket connect blocks until the server accepts
+    /// it. If the behavior is not expected, try `Socket::set_no_peercred`.
     pub fn connect(&self, address: &SockAddr) -> io::Result<()> {
         sys::connect(self.as_raw(), address)
     }
@@ -260,6 +263,11 @@ impl Socket {
     /// This function sets the same flags as in done for [`Socket::new`],
     /// [`Socket::accept_raw`] can be used if you don't want to set those flags.
     #[doc = man_links!(accept(2))]
+    ///
+    /// # Notes
+    ///
+    /// On Cygwin, a Unix domain socket connect blocks until the server accepts
+    /// it. If the behavior is not expected, try `Socket::set_no_peercred`.
     pub fn accept(&self) -> io::Result<(Socket, SockAddr)> {
         // Use `accept4` on platforms that support it.
         #[cfg(any(
@@ -271,6 +279,7 @@ impl Socket {
             target_os = "linux",
             target_os = "netbsd",
             target_os = "openbsd",
+            target_os = "cygwin",
         ))]
         return self._accept4(libc::SOCK_CLOEXEC);
 
@@ -284,6 +293,7 @@ impl Socket {
             target_os = "linux",
             target_os = "netbsd",
             target_os = "openbsd",
+            target_os = "cygwin",
         )))]
         {
             let (socket, addr) = self.accept_raw()?;
@@ -752,6 +762,7 @@ const fn set_common_type(ty: Type) -> Type {
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
+        target_os = "cygwin",
     ))]
     let ty = ty._cloexec();
 
@@ -781,6 +792,7 @@ fn set_common_flags(socket: Socket) -> io::Result<Socket> {
             target_os = "openbsd",
             target_os = "espidf",
             target_os = "vita",
+            target_os = "cygwin",
         ))
     ))]
     socket._set_cloexec(true)?;
@@ -956,7 +968,7 @@ impl Socket {
     /// For more information about this option, see [`set_passcred`].
     ///
     /// [`set_passcred`]: Socket::set_passcred
-    #[cfg(all(unix, target_os = "linux"))]
+    #[cfg(all(unix, any(target_os = "linux", target_os = "cygwin")))]
     pub fn passcred(&self) -> io::Result<bool> {
         unsafe {
             getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_PASSCRED)
@@ -968,7 +980,7 @@ impl Socket {
     ///
     /// If this option is enabled, enables the receiving of the `SCM_CREDENTIALS`
     /// control messages.
-    #[cfg(all(unix, target_os = "linux"))]
+    #[cfg(all(unix, any(target_os = "linux", target_os = "cygwin")))]
     pub fn set_passcred(&self, passcred: bool) -> io::Result<()> {
         unsafe {
             setsockopt(
@@ -1254,6 +1266,7 @@ impl Socket {
         target_os = "nto",
         target_os = "espidf",
         target_os = "vita",
+        target_os = "cygwin",
     )))]
     pub fn join_multicast_v4_n(
         &self,
@@ -1287,6 +1300,7 @@ impl Socket {
         target_os = "nto",
         target_os = "espidf",
         target_os = "vita",
+        target_os = "cygwin",
     )))]
     pub fn leave_multicast_v4_n(
         &self,
@@ -1577,6 +1591,7 @@ impl Socket {
         target_os = "nto",
         target_os = "espidf",
         target_os = "vita",
+        target_os = "cygwin",
     )))]
     pub fn set_recv_tos_v4(&self, recv_tos: bool) -> io::Result<()> {
         unsafe {
@@ -1608,6 +1623,7 @@ impl Socket {
         target_os = "nto",
         target_os = "espidf",
         target_os = "vita",
+        target_os = "cygwin",
     )))]
     pub fn recv_tos_v4(&self) -> io::Result<bool> {
         unsafe {
@@ -1978,6 +1994,7 @@ impl Socket {
             target_os = "hurd",
             target_os = "espidf",
             target_os = "vita",
+            target_os = "cygwin",
         ))
     ))]
     pub fn recv_hoplimit_v6(&self) -> io::Result<bool> {
@@ -2006,6 +2023,7 @@ impl Socket {
             target_os = "hurd",
             target_os = "espidf",
             target_os = "vita",
+            target_os = "cygwin",
         ))
     ))]
     pub fn set_recv_hoplimit_v6(&self, recv_hoplimit: bool) -> io::Result<()> {
@@ -2063,6 +2081,7 @@ impl Socket {
             target_os = "netbsd",
             target_os = "tvos",
             target_os = "watchos",
+            target_os = "cygwin",
         )
     ))]
     pub fn keepalive_interval(&self) -> io::Result<Duration> {
@@ -2092,6 +2111,7 @@ impl Socket {
             target_os = "netbsd",
             target_os = "tvos",
             target_os = "watchos",
+            target_os = "cygwin",
         )
     ))]
     pub fn keepalive_retries(&self) -> io::Result<u32> {
diff --git a/src/sys/unix.rs b/src/sys/unix.rs
index 8e24f4e5..bc808f11 100644
--- a/src/sys/unix.rs
+++ b/src/sys/unix.rs
@@ -72,6 +72,7 @@ use std::{io, slice};
     target_os = "macos",
     target_os = "tvos",
     target_os = "watchos",
+    target_os = "cygwin",
 )))]
 use libc::ssize_t;
 use libc::{in6_addr, in_addr};
@@ -140,6 +141,7 @@ pub(crate) use libc::IPV6_HDRINCL;
         target_os = "haiku",
         target_os = "espidf",
         target_os = "vita",
+        target_os = "cygwin",
     ))
 ))]
 pub(crate) use libc::IPV6_RECVHOPLIMIT;
@@ -173,6 +175,7 @@ pub(crate) use libc::IP_HDRINCL;
     target_os = "nto",
     target_os = "espidf",
     target_os = "vita",
+    target_os = "cygwin",
 )))]
 pub(crate) use libc::IP_RECVTOS;
 #[cfg(not(any(
@@ -199,7 +202,7 @@ pub(crate) use libc::SO_LINGER;
     target_os = "watchos",
 ))]
 pub(crate) use libc::SO_LINGER_SEC as SO_LINGER;
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "cygwin"))]
 pub(crate) use libc::SO_PASSCRED;
 pub(crate) use libc::{
     ip_mreq as IpMreq, linger, IPPROTO_IP, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, IPV6_MULTICAST_IF,
@@ -271,6 +274,7 @@ pub(crate) use libc::{
         target_os = "netbsd",
         target_os = "tvos",
         target_os = "watchos",
+        target_os = "cygwin",
     )
 ))]
 pub(crate) use libc::{TCP_KEEPCNT, TCP_KEEPINTVL};
@@ -278,6 +282,8 @@ pub(crate) use libc::{TCP_KEEPCNT, TCP_KEEPINTVL};
 // See this type in the Windows file.
 pub(crate) type Bool = c_int;
 
+#[cfg(target_os = "cygwin")]
+use libc::SO_PEERCRED;
 #[cfg(any(
     target_os = "ios",
     target_os = "visionos",
@@ -320,6 +326,7 @@ macro_rules! syscall {
     target_os = "macos",
     target_os = "tvos",
     target_os = "watchos",
+    target_os = "cygwin",
 )))]
 const MAX_BUF_LEN: usize = ssize_t::MAX as usize;
 
@@ -337,6 +344,7 @@ const MAX_BUF_LEN: usize = ssize_t::MAX as usize;
     target_os = "macos",
     target_os = "tvos",
     target_os = "watchos",
+    target_os = "cygwin",
 ))]
 const MAX_BUF_LEN: usize = c_int::MAX as usize - 1;
 
@@ -383,6 +391,7 @@ type IovLen = usize;
     target_os = "watchos",
     target_os = "espidf",
     target_os = "vita",
+    target_os = "cygwin",
 ))]
 type IovLen = c_int;
 
@@ -425,7 +434,8 @@ impl Type {
             target_os = "illumos",
             target_os = "linux",
             target_os = "netbsd",
-            target_os = "openbsd"
+            target_os = "openbsd",
+            target_os = "cygwin",
         )
     ))]
     pub const fn nonblocking(self) -> Type {
@@ -447,6 +457,7 @@ impl Type {
             target_os = "openbsd",
             target_os = "redox",
             target_os = "solaris",
+            target_os = "cygwin",
         )
     ))]
     pub const fn cloexec(self) -> Type {
@@ -465,6 +476,7 @@ impl Type {
         target_os = "openbsd",
         target_os = "redox",
         target_os = "solaris",
+        target_os = "cygwin",
     ))]
     pub(crate) const fn _cloexec(self) -> Type {
         Type(self.0 | libc::SOCK_CLOEXEC)
@@ -578,7 +590,10 @@ impl RecvFlags {
     /// on the local host.
     ///
     /// On Unix this corresponds to the `MSG_DONTROUTE` flag.
-    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+    ))]
     pub const fn is_dontroute(self) -> bool {
         self.0 & libc::MSG_DONTROUTE != 0
     }
@@ -595,7 +610,10 @@ impl std::fmt::Debug for RecvFlags {
         s.field("is_truncated", &self.is_truncated());
         #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
         s.field("is_confirm", &self.is_confirm());
-        #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+        #[cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        ))]
         s.field("is_dontroute", &self.is_dontroute());
         s.finish()
     }
@@ -767,7 +785,7 @@ impl SockAddr {
                     // Abstract addresses only exist on Linux.
                     // NOTE: although Fuchsia does define `AF_UNIX` it's not actually implemented.
                     // See https://github.com/rust-lang/socket2/pull/403#discussion_r1123557978
-                    || (cfg!(not(any(target_os = "linux", target_os = "android")))
+                    || (cfg!(not(any(target_os = "linux", target_os = "android", target_os = "cygwin")))
                     && storage.sun_path[0] == 0)
             })
             .unwrap_or_default()
@@ -840,14 +858,14 @@ impl SockAddr {
     pub fn as_abstract_namespace(&self) -> Option<&[u8]> {
         // NOTE: although Fuchsia does define `AF_UNIX` it's not actually implemented.
         // See https://github.com/rust-lang/socket2/pull/403#discussion_r1123557978
-        #[cfg(any(target_os = "linux", target_os = "android"))]
+        #[cfg(any(target_os = "linux", target_os = "android", target_os = "cygwin"))]
         {
             self.as_sockaddr_un().and_then(|storage| {
                 (self.len() > offset_of_path(storage) as _ && storage.sun_path[0] == 0)
                     .then(|| self.path_bytes(storage, true))
             })
         }
-        #[cfg(not(any(target_os = "linux", target_os = "android")))]
+        #[cfg(not(any(target_os = "linux", target_os = "android", target_os = "cygwin")))]
         None
     }
 }
@@ -1200,6 +1218,7 @@ pub(crate) fn set_tcp_keepalive(fd: Socket, keepalive: &TcpKeepalive) -> io::Res
         target_os = "netbsd",
         target_os = "tvos",
         target_os = "watchos",
+        target_os = "cygwin",
     ))]
     {
         if let Some(interval) = keepalive.interval {
@@ -1333,6 +1352,7 @@ pub(crate) fn from_in6_addr(addr: in6_addr) -> Ipv6Addr {
     target_os = "nto",
     target_os = "espidf",
     target_os = "vita",
+    target_os = "cygwin",
 )))]
 pub(crate) const fn to_mreqn(
     multiaddr: &Ipv4Addr,
@@ -1414,6 +1434,7 @@ impl crate::Socket {
             target_os = "linux",
             target_os = "netbsd",
             target_os = "openbsd",
+            target_os = "cygwin",
         )
     ))]
     pub fn accept4(&self, flags: c_int) -> io::Result<(crate::Socket, SockAddr)> {
@@ -1429,6 +1450,7 @@ impl crate::Socket {
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
+        target_os = "cygwin",
     ))]
     pub(crate) fn _accept4(&self, flags: c_int) -> io::Result<(crate::Socket, SockAddr)> {
         // Safety: `accept4` initialises the `SockAddr` for us.
@@ -1479,6 +1501,28 @@ impl crate::Socket {
         }
     }
 
+    /// Sets `SO_PEERCRED` to null on the socket.
+    /// This is a Cygwin extension.
+    ///
+    /// Normally the Unix domain sockets of Cygwin are implemented by TCP sockets,
+    /// so it performs a handshake on `connect` and `accept`, to verify the remote
+    /// connection and exchange peer cred info. Therefore, `connect` blocks until
+    /// the server `accept`s it. This option turns off the handshake. Both client
+    /// and server should turn it off to let `connect` returns immediately.
+    ///
+    /// See also: the [mailing list](https://inbox.sourceware.org/cygwin/TYCPR01MB10926FF8926CA63704867ADC8F8AA2@TYCPR01MB10926.jpnprd01.prod.outlook.com/)
+    #[cfg(target_os = "cygwin")]
+    pub fn set_no_peercred(&self) -> io::Result<()> {
+        syscall!(setsockopt(
+            self.as_raw(),
+            SOL_SOCKET,
+            SO_PEERCRED,
+            ptr::null_mut(),
+            0,
+        ))
+        .map(|_| ())
+    }
+
     /// Sets `SO_NOSIGPIPE` on the socket.
     #[cfg(all(
         feature = "all",
@@ -1551,6 +1595,7 @@ impl crate::Socket {
             target_os = "freebsd",
             target_os = "fuchsia",
             target_os = "linux",
+            target_os = "cygwin",
         )
     ))]
     pub fn is_listener(&self) -> io::Result<bool> {
@@ -1680,7 +1725,12 @@ impl crate::Socket {
     /// [`set_quickack`]: crate::Socket::set_quickack
     #[cfg(all(
         feature = "all",
-        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        any(
+            target_os = "android",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "cygwin",
+        )
     ))]
     pub fn quickack(&self) -> io::Result<bool> {
         unsafe {
@@ -1697,7 +1747,12 @@ impl crate::Socket {
     /// internal protocol processing and factors such as delayed ack timeouts occurring and data transfer.
     #[cfg(all(
         feature = "all",
-        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        any(
+            target_os = "android",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "cygwin",
+        )
     ))]
     pub fn set_quickack(&self, quickack: bool) -> io::Result<()> {
         unsafe {
@@ -1956,7 +2011,7 @@ impl crate::Socket {
     /// [`set_reuse_port`]: crate::Socket::set_reuse_port
     #[cfg(all(
         feature = "all",
-        not(any(target_os = "solaris", target_os = "illumos"))
+        not(any(target_os = "solaris", target_os = "illumos", target_os = "cygwin"))
     ))]
     pub fn reuse_port(&self) -> io::Result<bool> {
         unsafe {
@@ -1972,7 +2027,7 @@ impl crate::Socket {
     /// there's a socket already listening on this port.
     #[cfg(all(
         feature = "all",
-        not(any(target_os = "solaris", target_os = "illumos"))
+        not(any(target_os = "solaris", target_os = "illumos", target_os = "cygwin"))
     ))]
     pub fn set_reuse_port(&self, reuse: bool) -> io::Result<()> {
         unsafe {
@@ -2272,7 +2327,12 @@ impl crate::Socket {
     /// approximately 49.71 days.
     #[cfg(all(
         feature = "all",
-        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        any(
+            target_os = "android",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "cygwin",
+        )
     ))]
     pub fn set_tcp_user_timeout(&self, timeout: Option<Duration>) -> io::Result<()> {
         let timeout = timeout.map_or(0, |to| {
@@ -2295,7 +2355,12 @@ impl crate::Socket {
     /// [`set_tcp_user_timeout`]: crate::Socket::set_tcp_user_timeout
     #[cfg(all(
         feature = "all",
-        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        any(
+            target_os = "android",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "cygwin",
+        )
     ))]
     pub fn tcp_user_timeout(&self) -> io::Result<Option<Duration>> {
         unsafe {
@@ -2369,7 +2434,8 @@ impl crate::Socket {
             target_os = "linux",
             target_os = "macos",
             target_os = "netbsd",
-            target_os = "openbsd"
+            target_os = "openbsd",
+            target_os = "cygwin",
         )
     ))]
     pub fn tclass_v6(&self) -> io::Result<u32> {
@@ -2393,7 +2459,8 @@ impl crate::Socket {
             target_os = "linux",
             target_os = "macos",
             target_os = "netbsd",
-            target_os = "openbsd"
+            target_os = "openbsd",
+            target_os = "cygwin",
         )
     ))]
     pub fn set_tclass_v6(&self, tclass: u32) -> io::Result<()> {
diff --git a/tests/socket.rs b/tests/socket.rs
index a2dca668..77e30d35 100644
--- a/tests/socket.rs
+++ b/tests/socket.rs
@@ -186,7 +186,10 @@ fn socket_address_unix_unnamed() {
 }
 
 #[test]
-#[cfg(all(any(target_os = "linux", target_os = "android"), feature = "all"))]
+#[cfg(all(
+    any(target_os = "linux", target_os = "android", target_os = "cygwin"),
+    feature = "all",
+))]
 fn socket_address_unix_abstract_namespace() {
     let path = "\0h".repeat(108 / 2);
     let addr = SockAddr::unix(&path).unwrap();
@@ -568,10 +571,14 @@ fn unix() {
     let addr = SockAddr::unix(path).unwrap();
 
     let listener = Socket::new(Domain::UNIX, Type::STREAM, None).unwrap();
+    #[cfg(target_os = "cygwin")]
+    listener.set_no_peercred().unwrap();
     listener.bind(&addr).unwrap();
     listener.listen(10).unwrap();
 
     let mut a = Socket::new(Domain::UNIX, Type::STREAM, None).unwrap();
+    #[cfg(target_os = "cygwin")]
+    a.set_no_peercred().unwrap();
     a.connect(&addr).unwrap();
     let mut b = listener.accept().unwrap().0;
 
@@ -1247,6 +1254,7 @@ fn r#type() {
             target_os = "tvos",
             target_os = "watchos",
             target_os = "vita",
+            target_os = "cygwin",
         )),
         feature = "all",
     ))]
@@ -1356,12 +1364,21 @@ test!(out_of_band_inline, set_out_of_band_inline(true));
 test!(reuse_address, set_reuse_address(true));
 #[cfg(all(
     feature = "all",
-    not(any(windows, target_os = "solaris", target_os = "illumos"))
+    not(any(
+        windows,
+        target_os = "solaris",
+        target_os = "illumos",
+        target_os = "cygwin",
+    ))
 ))]
 test!(reuse_port, set_reuse_port(true));
 #[cfg(all(feature = "all", target_os = "freebsd"))]
 test!(reuse_port_lb, set_reuse_port_lb(true));
-#[cfg(all(feature = "all", unix, not(target_os = "redox")))]
+#[cfg(all(
+    feature = "all",
+    unix,
+    not(any(target_os = "redox", target_os = "cygwin")),
+))]
 test!(
     #[cfg_attr(target_os = "linux", ignore = "Different value returned")]
     mss,
@@ -1413,6 +1430,7 @@ test!(IPv4 ttl_v4, set_ttl_v4(40));
     target_os = "solaris",
     target_os = "illumos",
     target_os = "haiku",
+    target_os = "cygwin",
 )))]
 test!(IPv4 tos_v4, set_tos_v4(96));
 
@@ -1428,10 +1446,11 @@ test!(IPv4 tos_v4, set_tos_v4(96));
     target_os = "windows",
     target_os = "vita",
     target_os = "haiku",
+    target_os = "cygwin",
 )))]
 test!(IPv4 recv_tos_v4, set_recv_tos_v4(true));
 
-#[cfg(not(windows))] // TODO: returns `WSAENOPROTOOPT` (10042) on Windows.
+#[cfg(not(any(windows, target_os = "cygwin")))] // TODO: returns `WSAENOPROTOOPT` (10042) on Windows.
 test!(IPv4 broadcast, set_broadcast(true));
 
 #[cfg(not(target_os = "vita"))]
@@ -1442,11 +1461,12 @@ test!(IPv6 unicast_hops_v6, set_unicast_hops_v6(20));
     target_os = "dragonfly",
     target_os = "freebsd",
     target_os = "openbsd",
-    target_os = "vita"
+    target_os = "vita",
+    target_os = "cygwin",
 )))]
 test!(IPv6 only_v6, set_only_v6(true));
 // IPv6 socket are already IPv6 only on FreeBSD and Windows.
-#[cfg(any(windows, target_os = "freebsd"))]
+#[cfg(any(windows, target_os = "freebsd", target_os = "cygwin"))]
 test!(IPv6 only_v6, set_only_v6(false));
 
 #[cfg(all(
@@ -1476,6 +1496,7 @@ test!(IPv6 tclass_v6, set_tclass_v6(96));
     target_os = "windows",
     target_os = "vita",
     target_os = "haiku",
+    target_os = "cygwin",
 )))]
 test!(IPv6 recv_tclass_v6, set_recv_tclass_v6(true));
 
@@ -1493,6 +1514,7 @@ test!(IPv6 recv_tclass_v6, set_recv_tclass_v6(true));
         target_os = "windows",
         target_os = "vita",
         target_os = "haiku",
+        target_os = "cygwin",
     ))
 ))]
 test!(IPv6 recv_hoplimit_v6, set_recv_hoplimit_v6(true));
@@ -1520,6 +1542,7 @@ test!(IPv6 multicast_all_v6, set_multicast_all_v6(false));
     target_os = "redox",
     target_os = "solaris",
     target_os = "vita",
+    target_os = "cygwin",
 )))]
 fn join_leave_multicast_v4_n() {
     let socket = Socket::new(Domain::IPV4, Type::DGRAM, None).unwrap();