This article explains how to unpair your Apple Watch from your iPhone, using your iPhone or Apple Watch. Information applies to Apple Watches running watchOS 6 or later and to the iPhone Watch app in iOS 15 through iOS 10.
How to Unpair and Reset Your Apple Watch | Apple Support
You may want to unpair your Apple Watch from your iPhone if you plan to sell or give away your watch, or if you plan to buy a newer watch. Here's how to unpair your Apple Watch using your iPhone.
Tap the Apple Watch app on your iPhone.
At the top of the screen, tap All Watches (or My Watch).
