A phone's wireless charger won't charge the watch
A flat Qi pad or a MagSafe phone puck is built to push power into the back of a phone. The watch charges from a small magnetic puck that snaps onto the back of its case instead.
When a watch won't charge, Apple's first instruction is to "Make sure you're using the Apple Magnetic Charging Cable or USB-C Magnetic Fast Charging Cable that came with your watch." A general phone pad isn't mentioned.
What Apple actually lists as a charger for it
Beyond the cable in the box, Apple's support page names the Apple Watch Magnetic Charging Dock and the Apple MagSafe Duo Charger. It also mentions "a WPT-compliant charger purchased in China or Indonesia", and says an incompatible Apple Watch on one of those shows a message. That's a regional exception, tied to where the charger was bought.
Fast charging tightens the requirements again
Apple says "Fast charging is supported on Apple Watch Series 7 and later, Apple Watch SE 3, and Apple Watch Ultra and later". It "requires an Apple USB-C Magnetic Fast Charging Cable", fed by a USB-C power adapter; for a third-party one, Apple asks for "a comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD) of 5W or greater." Apple also notes that "WPT-compliant chargers don't support fast charging", so even the WPT charger Apple recognises only tops the watch up at the ordinary rate. An older watch, or the older non-USB-C cable, charges at that ordinary rate whatever you feed it.
What this means for a one-charger desk
One base can charge a phone and a watch, but only by giving the watch its own magnetic spot. Apple's MagSafe Duo works that way, charging "your iPhone 12, iPhone 13, or iPhone 14 and your Apple Watch simultaneously" from one unit with a separate place for each. On any 3-in-1 stand, check what the listing says about the watch spot: that it's a magnetic watch charger, and whether it fast charges your model. Our best 3-in-1 wireless charger guide covers the stands that take a phone, a watch and earbuds. If the Qi, Qi2 and MagSafe labels are the confusing part, our Qi2 vs MagSafe explainer sorts them out.
FAQ
Q: Will the Apple Watch charger charge my iPhone? A: No, and Apple doesn't list it for that. The puck is shaped to the back of the watch, so the two chargers aren't interchangeable in either direction.
Q: Does the Apple Watch come with a charger? A: It comes with the magnetic charging cable Apple tells you to use.