If you can't remember your username, follow these steps to retrieve it:
Visit the Gmail username-recovery page.
Choose to recover your username using either the backup email address or phone number you listed when signing up for Gmail.
Enter the name on the account.
Type the letters in the distorted picture and click Submit.
We’ll send you a list of usernames associated with the email or phone number you entered. If you entered a:
Recovery email: A list of any usernames associated with that email address will be sent to it.
Recovery phone number: We’ll send a verification code to that phone via text or call. Enter the code and click Continue. We’ll show you the usernames associated with that phone number on the next page.
If you didn't enter an alternate email address when you created your Gmail address, but you were invited to Gmail, you may be able to retrieve your username by clicking the link in your Gmail invitation.