If you forget your Apple Watch Ultra passcode
If your Apple Watch Ultra is disabled because you forgot your passcode or entered an incorrect passcode too many times, you can reset it from either your Apple Watch Ultra or iPhone and set it up again.
Important: If Erase Data is turned on, the data on your Apple Watch Ultra is erased after 10 failed passcode attempts.
Reset your Apple Watch Ultra
Put your Apple Watch Ultra on its charger, then press and hold the side button until the sliders appear.
Press and hold the Digital Crown to show the Erase all content and settings screen.
Tap Reset, then tap Reset again to confirm.
When the process finishes, set up your watch again. When asked, restore from a backup.
Reset your Apple Watch Ultra using your paired iPhone
Open the Apple Watch app on your iPhone, then tap My Watch.
Tap General, swipe down, then tap Reset.
Tap Erase Apple Watch Content and Settings, then tap Erase All Content and Settings again to confirm.
If you have a cellular plan, choose to keep or remove it.
Keep your plan if you want to pair your Apple Watch Ultra and iPhone again.
Remove your plan if you want to pair your Apple Watch Ultra with another iPhone or intend to cancel your cellular subscription. (Contact your carrier to cancel your subscription.)
When the process finishes, set up your watch again. When asked, restore from a backup.
When you erase Apple Watch Ultra this way, Activation Lock is enabled. With Activation Lock, your Apple ID and password are required before anyone can:
Unpair your Apple Watch from your iPhone.
Pair and use your Apple Watch with a new iPhone.
Turn off Find My on your device.
See the Apple Support article About Activation Lock on your Apple Watch.