diff --git a/Help/manual/cmake-variables.7.rst b/Help/manual/cmake-variables.7.rst
index de4ce3debc..5a16795b16 100644
--- a/Help/manual/cmake-variables.7.rst
+++ b/Help/manual/cmake-variables.7.rst
@@ -276,6 +276,7 @@ Variables that Describe the System
    /variable/MSVC_IDE
    /variable/MSVC_TOOLSET_VERSION
    /variable/MSVC_VERSION
+   /variable/MSYS
    /variable/UNIX
    /variable/WIN32
    /variable/WINCE
diff --git a/Help/variable/MSYS.rst b/Help/variable/MSYS.rst
new file mode 100644
index 0000000000..25ddc7f739
--- /dev/null
+++ b/Help/variable/MSYS.rst
@@ -0,0 +1,4 @@
+MSYS
+----
+
+``True`` when using the :generator:`MSYS Makefiles` generator.