Keep your Apple Watch and iPhone close together
Open the Watch app on your iPhone
Tap All Watches
Tap the info button next to your Apple Watch
Tap Unpair Apple Watch
Enter your Apple ID password if prompted
Tap Unpair to confirm
Wait for the unpairing process to finish
If needed, erase the Apple Watch from Settings on the watch itself
If you do not have the paired iPhone, erase the Apple Watch from the watch’s Settings app
If you want to pair it again later, set it up as a new watch or restore from backup