diff --git a/GNUmakefile b/GNUmakefile
index 6f5eda35f30..d3430e7e2e5 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -62,15 +62,15 @@ TOYBOX_SRC  := $(TOYBOX_ROOT)/toybox-$(TOYBOX_VER)
 
 #------------------------------------------------------------------------
 # Detect the host system.
-# On Windows the environment already sets  OS = Windows_NT.
+# On Windows uname -s might return MINGW_NT-* or CYGWIN_NT-*.
 # Otherwise let it default to the kernel name returned by uname -s
 # (Linux, Darwin, FreeBSD, …).
 #------------------------------------------------------------------------
-OS ?= $(shell uname -s)
+OS := $(shell uname -s)
 
 # Windows does not allow symlink by default.
 # Allow to override LN for AppArmor.
-ifeq ($(OS),Windows_NT)
+ifneq (,$(findstring _NT,$(OS)))
 	LN ?= ln -f
 endif
 LN ?= ln -sf
@@ -195,7 +195,7 @@ HASHSUM_PROGS := \
 
 $(info Detected OS = $(OS))
 
-ifneq ($(OS),Windows_NT)
+ifeq (,$(findstring MINGW,$(OS)))
 	PROGS += $(UNIX_PROGS)
 endif
 ifeq ($(SELINUX_ENABLED),1)
@@ -450,8 +450,12 @@ install: build install-manpages install-completions install-locales
 	mkdir -p $(INSTALLDIR_BIN)
 ifneq (,$(and $(findstring stdbuf,$(UTILS)),$(findstring feat_external_libstdbuf,$(CARGOFLAGS))))
 	mkdir -p $(DESTDIR)$(LIBSTDBUF_DIR)
+ifneq (,$(findstring CYGWIN,$(OS)))
+	$(INSTALL) -m 755 $(BUILDDIR)/deps/stdbuf.dll $(DESTDIR)$(LIBSTDBUF_DIR)/libstdbuf.dll
+else
 	$(INSTALL) -m 755 $(BUILDDIR)/deps/libstdbuf.* $(DESTDIR)$(LIBSTDBUF_DIR)/
 endif
+endif
 ifeq (${MULTICALL}, y)
 	$(INSTALL) -m 755 $(BUILDDIR)/coreutils $(INSTALLDIR_BIN)/$(PROG_PREFIX)coreutils
 	$(foreach prog, $(filter-out coreutils, $(INSTALLEES)), \
@@ -472,7 +476,7 @@ else
 endif
 
 uninstall:
-ifneq ($(OS),Windows_NT)
+ifeq (,$(findstring MINGW,$(OS)))
 	rm -f $(DESTDIR)$(LIBSTDBUF_DIR)/libstdbuf.*
 	-rm -d $(DESTDIR)$(LIBSTDBUF_DIR) 2>/dev/null || true
 endif
diff --git a/src/uu/chroot/src/chroot.rs b/src/uu/chroot/src/chroot.rs
index 6f615885054..289511d81c5 100644
--- a/src/uu/chroot/src/chroot.rs
+++ b/src/uu/chroot/src/chroot.rs
@@ -319,7 +319,12 @@ fn supplemental_gids(uid: libc::uid_t) -> Vec<libc::gid_t> {
 
 /// Set the supplemental group IDs for this process.
 fn set_supplemental_gids(gids: &[libc::gid_t]) -> std::io::Result<()> {
-    #[cfg(any(target_vendor = "apple", target_os = "freebsd", target_os = "openbsd"))]
+    #[cfg(any(
+        target_vendor = "apple",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "cygwin"
+    ))]
     let n = gids.len() as libc::c_int;
     #[cfg(any(target_os = "linux", target_os = "android"))]
     let n = gids.len() as libc::size_t;
diff --git a/src/uu/id/src/id.rs b/src/uu/id/src/id.rs
index 298619fd5e3..59f06809af5 100644
--- a/src/uu/id/src/id.rs
+++ b/src/uu/id/src/id.rs
@@ -535,7 +535,12 @@ fn pline(possible_uid: Option<uid_t>) {
     );
 }
 
-#[cfg(any(target_os = "linux", target_os = "android", target_os = "openbsd"))]
+#[cfg(any(
+    target_os = "linux",
+    target_os = "android",
+    target_os = "openbsd",
+    target_os = "cygwin"
+))]
 fn pline(possible_uid: Option<uid_t>) {
     let uid = possible_uid.unwrap_or_else(getuid);
     let pw = Passwd::locate(uid).unwrap();
@@ -552,10 +557,20 @@ fn pline(possible_uid: Option<uid_t>) {
     );
 }
 
-#[cfg(any(target_os = "linux", target_os = "android", target_os = "openbsd"))]
+#[cfg(any(
+    target_os = "linux",
+    target_os = "android",
+    target_os = "openbsd",
+    target_os = "cygwin"
+))]
 fn auditid() {}
 
-#[cfg(not(any(target_os = "linux", target_os = "android", target_os = "openbsd")))]
+#[cfg(not(any(
+    target_os = "linux",
+    target_os = "android",
+    target_os = "openbsd",
+    target_os = "cygwin"
+)))]
 fn auditid() {
     use std::mem::MaybeUninit;
 
diff --git a/src/uu/nohup/src/nohup.rs b/src/uu/nohup/src/nohup.rs
index 38b5e5ceb30..6280d44e1e3 100644
--- a/src/uu/nohup/src/nohup.rs
+++ b/src/uu/nohup/src/nohup.rs
@@ -185,7 +185,8 @@ unsafe extern "C" {
     target_os = "linux",
     target_os = "android",
     target_os = "freebsd",
-    target_os = "openbsd"
+    target_os = "openbsd",
+    target_os = "cygwin"
 ))]
 /// # Safety
 /// This function is unsafe because it dereferences a raw pointer.
diff --git a/src/uu/stdbuf/build.rs b/src/uu/stdbuf/build.rs
index aa2692cb512..d844f37907a 100644
--- a/src/uu/stdbuf/build.rs
+++ b/src/uu/stdbuf/build.rs
@@ -26,6 +26,11 @@ mod platform {
     pub const DYLIB_EXT: &str = ".dylib";
 }
 
+#[cfg(target_os = "cygwin")]
+mod platform {
+    pub const DYLIB_EXT: &str = ".dll";
+}
+
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=src/libstdbuf/src/libstdbuf.rs");
@@ -103,6 +108,9 @@ fn main() {
     assert!(status.success(), "Failed to build libstdbuf");
 
     // Copy the built library to OUT_DIR for include_bytes! to find
+    #[cfg(target_os = "cygwin")]
+    let lib_name = format!("stdbuf{}", platform::DYLIB_EXT);
+    #[cfg(not(target_os = "cygwin"))]
     let lib_name = format!("libstdbuf{}", platform::DYLIB_EXT);
     let dest_path = Path::new(&out_dir).join(format!("libstdbuf{}", platform::DYLIB_EXT));
 
diff --git a/src/uu/stdbuf/src/libstdbuf/build.rs b/src/uu/stdbuf/src/libstdbuf/build.rs
index 505cdf68aec..7584bf31f8e 100644
--- a/src/uu/stdbuf/src/libstdbuf/build.rs
+++ b/src/uu/stdbuf/src/libstdbuf/build.rs
@@ -11,8 +11,8 @@ fn main() {
     println!("cargo:rustc-link-arg=-fPIC");
 
     let target = env::var("TARGET").unwrap_or_else(|_| "unknown".to_string());
-    // Ensure the library doesn't have any undefined symbols (-z flag not supported on macOS)
-    if !target.contains("apple-darwin") {
+    // Ensure the library doesn't have any undefined symbols (-z flag not supported on macOS and Cygwin)
+    if !target.contains("apple-darwin") && !target.contains("cygwin") {
         println!("cargo:rustc-link-arg=-z");
         println!("cargo:rustc-link-arg=defs");
     }
diff --git a/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs b/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs
index 3ef7473bf79..da0e43fef0c 100644
--- a/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs
+++ b/src/uu/stdbuf/src/libstdbuf/src/libstdbuf.rs
@@ -2,7 +2,7 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
-// spell-checker:ignore (ToDO) IOFBF IOLBF IONBF setvbuf stderrp stdinp stdoutp
+// spell-checker:ignore (ToDO) getreent reent IOFBF IOLBF IONBF setvbuf stderrp stdinp stdoutp
 
 use ctor::ctor;
 use libc::{_IOFBF, _IOLBF, _IONBF, FILE, c_char, c_int, fileno, size_t};
@@ -35,7 +35,35 @@ pub unsafe extern "C" fn __stdbuf_get_stdin() -> *mut FILE {
         unsafe { __stdin }
     }
 
-    #[cfg(not(any(target_os = "macos", target_os = "freebsd", target_os = "openbsd")))]
+    #[cfg(target_os = "cygwin")]
+    {
+        // _getreent()->_std{in,out,err}
+        // see:
+        // echo '#include <stdio.h>\nstd{in,out,err}' | gcc -E -xc - -std=c23 | tail -n1
+        // echo '#include <stdio.h>' | grep -E -xc - -std=c23 | grep 'struct _reent' -A91 | grep 580 -A91 | tail -n+2
+
+        #[repr(C)]
+        struct _reent {
+            _errno: c_int,
+            _stdin: *mut FILE,
+            _stdout: *mut FILE,
+            _stderr: *mut FILE,
+            // other stuff
+        }
+
+        unsafe extern "C" {
+            fn __getreent() -> *mut _reent;
+        }
+
+        unsafe { (*__getreent())._stdin }
+    }
+
+    #[cfg(not(any(
+        target_os = "macos",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "cygwin"
+    )))]
     {
         unsafe extern "C" {
             static mut stdin: *mut FILE;
@@ -64,7 +92,35 @@ pub unsafe extern "C" fn __stdbuf_get_stdout() -> *mut FILE {
         unsafe { __stdout }
     }
 
-    #[cfg(not(any(target_os = "macos", target_os = "freebsd", target_os = "openbsd")))]
+    #[cfg(target_os = "cygwin")]
+    {
+        // _getreent()->_std{in,out,err}
+        // see:
+        // echo '#include <stdio.h>\nstd{in,out,err}' | gcc -E -xc - -std=c23 | tail -n1
+        // echo '#include <stdio.h>' | grep -E -xc - -std=c23 | grep 'struct _reent' -A91 | grep 580 -A91 | tail -n+2
+
+        #[repr(C)]
+        struct _reent {
+            _errno: c_int,
+            _stdin: *mut FILE,
+            _stdout: *mut FILE,
+            _stderr: *mut FILE,
+            // other stuff
+        }
+
+        unsafe extern "C" {
+            fn __getreent() -> *mut _reent;
+        }
+
+        unsafe { (*__getreent())._stdout }
+    }
+
+    #[cfg(not(any(
+        target_os = "macos",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "cygwin"
+    )))]
     {
         unsafe extern "C" {
             static mut stdout: *mut FILE;
@@ -93,7 +149,35 @@ pub unsafe extern "C" fn __stdbuf_get_stderr() -> *mut FILE {
         unsafe { __stderr }
     }
 
-    #[cfg(not(any(target_os = "macos", target_os = "freebsd", target_os = "openbsd")))]
+    #[cfg(target_os = "cygwin")]
+    {
+        // _getreent()->_std{in,out,err}
+        // see:
+        // echo '#include <stdio.h>\nstd{in,out,err}' | gcc -E -xc - -std=c23 | tail -n1
+        // echo '#include <stdio.h>' | grep -E -xc - -std=c23 | grep 'struct _reent' -A91 | grep 580 -A91 | tail -n+2
+
+        #[repr(C)]
+        struct _reent {
+            _errno: c_int,
+            _stdin: *mut FILE,
+            _stdout: *mut FILE,
+            _stderr: *mut FILE,
+            // other stuff
+        }
+
+        unsafe extern "C" {
+            fn __getreent() -> *mut _reent;
+        }
+
+        unsafe { (*__getreent())._stdin }
+    }
+
+    #[cfg(not(any(
+        target_os = "macos",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "cygwin"
+    )))]
     {
         unsafe extern "C" {
             static mut stderr: *mut FILE;
diff --git a/src/uu/stdbuf/src/stdbuf.rs b/src/uu/stdbuf/src/stdbuf.rs
index 9af3d80cab1..f45dd2b97b3 100644
--- a/src/uu/stdbuf/src/stdbuf.rs
+++ b/src/uu/stdbuf/src/stdbuf.rs
@@ -43,6 +43,9 @@ const STDBUF_INJECT: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/libstdbuf
 #[cfg(all(not(feature = "feat_external_libstdbuf"), target_vendor = "apple"))]
 const STDBUF_INJECT: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/libstdbuf.dylib"));
 
+#[cfg(all(not(feature = "feat_external_libstdbuf"), target_os = "cygwin"))]
+const STDBUF_INJECT: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/libstdbuf.dll"));
+
 enum BufferType {
     Default,
     Line,
diff --git a/src/uu/stty/src/flags.rs b/src/uu/stty/src/flags.rs
index c10e7c04b39..d3f4ca848be 100644
--- a/src/uu/stty/src/flags.rs
+++ b/src/uu/stty/src/flags.rs
@@ -256,13 +256,16 @@ pub const LOCAL_FLAGS: &[Flag<L>] = &[
     // Not supported by nix
     // Flag::new("xcase", L::XCASE),
     Flag::new("tostop", L::TOSTOP),
+    #[cfg(not(target_os = "cygwin"))]
     Flag::new("echoprt", L::ECHOPRT),
+    #[cfg(not(target_os = "cygwin"))]
     Flag::new("prterase", L::ECHOPRT).hidden(),
     Flag::new("echoctl", L::ECHOCTL).sane(),
     Flag::new("ctlecho", L::ECHOCTL).sane().hidden(),
     Flag::new("echoke", L::ECHOKE).sane(),
     Flag::new("crtkill", L::ECHOKE).sane().hidden(),
     Flag::new("flusho", L::FLUSHO),
+    #[cfg(not(target_os = "cygwin"))]
     Flag::new("extproc", L::EXTPROC),
 ];
 
diff --git a/src/uucore/src/lib/features/utmpx.rs b/src/uucore/src/lib/features/utmpx.rs
index 8832caff3ba..3c3664389df 100644
--- a/src/uucore/src/lib/features/utmpx.rs
+++ b/src/uucore/src/lib/features/utmpx.rs
@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 //
-// spell-checker:ignore logind
+// spell-checker:ignore IDLEN logind
 
 //! Aims to provide platform-independent methods to obtain login records
 //!
@@ -56,7 +56,12 @@ pub use libc::getutxent;
 #[cfg_attr(target_env = "musl", allow(deprecated))]
 pub use libc::setutxent;
 use libc::utmpx;
-#[cfg(any(target_vendor = "apple", target_os = "linux", target_os = "netbsd"))]
+#[cfg(any(
+    target_vendor = "apple",
+    target_os = "linux",
+    target_os = "netbsd",
+    target_os = "cygwin"
+))]
 #[cfg_attr(target_env = "musl", allow(deprecated))]
 pub use libc::utmpxname;
 
@@ -179,6 +184,25 @@ mod ut {
     pub use libc::USER_PROCESS;
 }
 
+#[cfg(target_os = "cygwin")]
+mod ut {
+    pub static DEFAULT_FILE: &str = "";
+
+    pub use libc::UT_HOSTSIZE;
+    pub use libc::UT_IDLEN;
+    pub use libc::UT_LINESIZE;
+    pub use libc::UT_NAMESIZE;
+
+    pub use libc::BOOT_TIME;
+    pub use libc::DEAD_PROCESS;
+    pub use libc::INIT_PROCESS;
+    pub use libc::LOGIN_PROCESS;
+    pub use libc::NEW_TIME;
+    pub use libc::OLD_TIME;
+    pub use libc::RUN_LVL;
+    pub use libc::USER_PROCESS;
+}
+
 /// A login record
 pub struct Utmpx {
     inner: utmpx,