You can manage all your custom reports by using the Saved Reports page. There you can view a list of all your saved reports and edit, view or delete them.
Administrators can use this page to quickly delete or change ownership of reports. This can be especially useful when the owner of several reports leaves the organization.
Report ownership can only be transferred by an administrator, and only to a user with administration rights. Typically an administrator would transfer ownership of an ex-employee's reports to themself as part of normal housekeeping procedures.