Manual:$wgNamespaceAliases

Namespaces: $wgNamespaceAliases
Provide additional names for namespaces.
Introduced in version:	1.10.0 (r21720)
Removed in version:	still in use
Allowed values:	(array of strings)
Default value:	[]
Other settings: Alphabetical | By function

Details

These are alternate names for the primary localized namespace names, which are defined by $wgExtraNamespaces and the language file. If a page is requested with such a prefix, the request will be redirected to the primary name.

Set this to a map from namespace names to IDs. Example:

$wgNamespaceAliases = [
	'Wikipedian' => NS_USER,
	'Help' => 100
];

To add a single alias:

$wgNamespaceAliases['WP'] = NS_PROJECT;

If you need an alias for the project you probably need a similar alias for its talk page and you should add an array as above or two lines:

$wgNamespaceAliases['WP'] = NS_PROJECT;
$wgNamespaceAliases['WP_talk'] = NS_PROJECT_TALK;

Prior to MediaWiki 1.17, it was impossible to make an alias to NS_MAIN.

If this setting is set to a namespace that does not exist (e.g. the namespace has not been added to $wgExtraNamespaces but a constant has been defined) the alias will redirect to the main space.

Do not use spaces

Use underscores instead of spaces in namespace names. 'My Namespace' is an invalid name; use 'My_Namespace' instead.