You need to enter your Google Account email address and password to sign into YouTube. Note that a Google Account email address is not always a Gmail address.
If you forgot your password, you can visit the YouTube account recovery page to reset it.
Unless you have an old legacy account, your YouTube password is your Google Account password. If you reset your Google Account password, it will change for all Google services on that account, such as Gmail, Picasa, Blogger, Checkout, etc.
See our tips if you're having trouble resetting your Google Account password.
Forgot email address
If you can't remember your Google Account email address, try the Google account recovery page. Choose "I don't know my username." You'll be asked to enter the recovery email address you should have entered when signing up. If you never entered a recovery email address, we unfortunately can't help look up your Google Account email address.
Some older YouTube accounts are not part of a Google Account (this is only the case if you haven't signed into your account since before 2011). You can still sign into these legacy accounts with the YouTube username—just enter it into the "Email" field.