Native Apple Watch apps that can run independently of an iPhone are the biggest change, but there's also a nifty nightstand mode and some cool new watch face designs as well.
But how do you install it on your Apple Watch? Just follow our simple guide.
1. Get everything charged and your Apple Watch charger at the ready
2. Head to the Apple Watch app on your iPhone
3. Hit General and check software update
4. Install any outstanding updates
5. Hit download on the watchOS 2 update when it arrives
6. Enter your Apple Watch's passcode on your iPhone
7. Install and enjoy.
We're going to be updating our fantastic Apple Watch unofficial user's guide over the next week with tonnes of watchOS 2 tips and tricks, so check back. And make sure you follow our Apple Watch apps guide for the inside track on the latest and greatest native apps on for Apple's smartwatch.