diff --git a/share/mklocale/README.locale_name b/share/mklocale/README.locale_name
new file mode 100644
index 000000000000..f34cf67814cb
--- /dev/null
+++ b/share/mklocale/README.locale_name
@@ -0,0 +1,7 @@
+Locale name string format must be compliant with XPG3 and
+using following format.
+	<locale name>   ::= <language>_<territory>.<encoding>
+	<language>      ::= based on ISO 639
+	<territory>     ::= based on ISO 3166 (country code)
+	<encoding>      ::= "EUC", "KOI8-R", ...
+
diff --git a/usr.bin/mklocale/README.locale_name b/usr.bin/mklocale/README.locale_name
new file mode 100644
index 000000000000..f34cf67814cb
--- /dev/null
+++ b/usr.bin/mklocale/README.locale_name
@@ -0,0 +1,7 @@
+Locale name string format must be compliant with XPG3 and
+using following format.
+	<locale name>   ::= <language>_<territory>.<encoding>
+	<language>      ::= based on ISO 639
+	<territory>     ::= based on ISO 3166 (country code)
+	<encoding>      ::= "EUC", "KOI8-R", ...
+