Board Thread:Support Requests - Getting Technical/@comment-4996890-20130817022908/@comment-1330470-20130817025047

Wikia doesn't allow its individual wikis to have off-site URLs such as wolfensteinwiki.org (for example). In part because such domains cost money.

There are exceptions in the form of Very Large Wikis such as startrek and wow. These are deemed important enough (and moneymaking enough) to Wikia to justify their own domain names.

As has been said, you are free to purchase and maintain your own domain names, and redirect them to Wikia (as you would be free to redirect it anywhere). This would have to be done with your own funds.