The iOS 15 Device Support List – Can You Run the New OS?

In one sentence: If you can run iOS 14 you can run iOS 15. The iOS 15 device support list includes iPhone 6s and later.
iOS 15 Device Support List

iPhone 6S, iPhone 6S Plus
iPhone SE (2016), iPhone SE (2020)
iPhone 7, iPhone 7 Plus
iPhone 8, iPhone 8 Plus
iPhone X
iPhone XR
iPhone XS, iPhone XS Max
iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max
iPhone 12, iPhone 12 mini, iPhone 12 Pro, iPhone 12 Pro Max
iPod Touch (seventh generation)

Some features, like portrait mode in FaceTime, requires an iPhone with an A12 Bionic chip or newer. This means the iPhone XS or newer.
Tags: iOS 15, iPhone