Unlock phone

If you're talking about the passcode to access your iPhone:

If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support

If you're talking about the Apple ID password, follow the steps that QuickTimeKirk provided.

If you meant something different, please better describe your needs.

Regards

Giulio

https://iforgot.apple.com/password/verify/appleid