If you forgot your Grants.gov account username, you can complete the retrieve username process.
How to Retrieve a Username
Click the Login link in the upper-right corner of the Grants.gov banner.
Click the Forgot My Username link that is located beneath the Username and Password fields.
Enter your email address associated with this Grants.gov account in the Email Address field.
Click the Submit button. An email will be sent with your Grants.gov username to the email address you entered. Use this username to log in to Grants.gov.