How to Remove/Delete "Domain Name" from Salesforce org?

Hi Suraj,

You can’t delete a domain that is attached to a published site. You’ll need to unpublish all sites attached to the domain before you can delete it. For Force.com sites, the domain is deleted immediately, and users no longer have access to any site connected to that domain. But with Site.com sites, the domain remains active until you republish the site.

To delete a domain from your organization:
From Setup, enter Domains in the Quick Find box, then select Domains.
Click Del next to the domain name.
Click OK.
When you delete a domain with an unpublished site attached, it also deletes the custom URL associated with that site.

Thanks.