diff --git a/Help/manual/cmake-variables.7.rst b/Help/manual/cmake-variables.7.rst
index ce65aee8a5..9fc8a79617 100644
--- a/Help/manual/cmake-variables.7.rst
+++ b/Help/manual/cmake-variables.7.rst
@@ -322,6 +322,7 @@ Variables that Describe the System
    /variable/CYGWIN
    /variable/GHSMULTI
    /variable/IOS
+   /variable/LINUX
    /variable/MINGW
    /variable/MSVC
    /variable/MSVC10
diff --git a/Help/release/dev/LINUX.rst b/Help/release/dev/LINUX.rst
new file mode 100644
index 0000000000..45b70297ac
--- /dev/null
+++ b/Help/release/dev/LINUX.rst
@@ -0,0 +1,4 @@
+Variables
+---------
+
+* The :variable:`LINUX` variable is set to true when the target system is Linux.
diff --git a/Help/variable/LINUX.rst b/Help/variable/LINUX.rst
new file mode 100644
index 0000000000..26379b3d06
--- /dev/null
+++ b/Help/variable/LINUX.rst
@@ -0,0 +1,6 @@
+LINUX
+-----
+
+.. versionadded:: 3.25
+
+Set to true when the target system is Linux.
diff --git a/Modules/Platform/Linux.cmake b/Modules/Platform/Linux.cmake
index a7e58ab496..e3d444e96b 100644
--- a/Modules/Platform/Linux.cmake
+++ b/Modules/Platform/Linux.cmake
@@ -1,3 +1,4 @@
+set(LINUX 1)
 set(CMAKE_DL_LIBS "dl")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG "-Wl,-rpath,")
 set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG_SEP ":")
diff --git a/Modules/Platform/kFreeBSD.cmake b/Modules/Platform/kFreeBSD.cmake
index c1db2594d4..01ddfd39e0 100644
--- a/Modules/Platform/kFreeBSD.cmake
+++ b/Modules/Platform/kFreeBSD.cmake
@@ -1,4 +1,5 @@
 # kFreeBSD looks just like Linux.
 include(Platform/Linux)
+unset(LINUX)
 
 set(CMAKE_LIBRARY_ARCHITECTURE_REGEX "[a-z0-9_]+(-[a-z0-9_]+)?-kfreebsd-gnu[a-z0-9_]*")