If you are trying to "usurp" an existing username, please use the steward requests page.
Instructions
Read Wikipedia:Changing username carefully. You must be aware of and understand all the implications of changing your username. Specifically:
Your name will be changed to the new one in the page history of every page you've edited, and in all log entries.
Your user pages, account preferences, and edits will be moved to the new name. Please do not create a new account or attempt to move them yourself.
Links left by your previous signatures will still point to the old userpage; however, a redirect will be created pointing to your new userpage.
Understand that using your real name as your username may put you at risk of harassment. If you choose to do so, you must acknowledge the risks in your request.
Read the username policy and ensure your new name does not violate it. Usernames must not:
Check that your new username is not already in use by searching for it on Special:CentralAuth. If the name is registered, even on another Wikimedia project, it is taken. If the target name hasn't made any edits to any Wikimedia project, you may request usurpation at meta:Steward requests/Username changes.
Log in with your current username. Requests will not be approved if the requester is not logged in.
Add a reason for the change after REASON=. Requests without a valid reason will not be approved.
Do not change anything else.
Select Publish changes.
Check back on this page periodically to answer any inquiries regarding your request. Consider watching the page so you can monitor updates. Requests may be closed if there are unresolved queries.
Requests that do not follow these instructions or that are grossly malformed are subject to removal.
Completed and rejected requests will automatically be archived into one of the pages below.
Completed requests
Declined requests
CHUS completed}}
CHUS rejected}}
For stewards, global renamers, and clerks
Any experienced user is welcome to help clerk this page, such as to fix malformed requests and check for common issues. If you would like to help out with clerking, please see Wikipedia:Changing username/Assistance before clerking.
Reminders for clerks
Only stewards and global renamers have the authority to approve or decline requests. Please do not remove or decline requests yourself.
Compliant requests do not need a response. To avoid cluttering the page, please do not comment on them.
Please remember to check Special:CentralAuth to see if an account is subject to blocks on another project before renaming.
Please install User:Enterprisey/rename-reason-fixer to auto-populate the rename reason with a link to the request. This ensures a paper trail for the request is available.
Do not be surprised if you suddenly cannot log in to your old account; this merely indicates that you should log in under your new user name as the request has been fulfilled.