Apple Intelligence has launched with iOS 18.1: Here’s which iPhones are compatible
You’ll need an iPhone with an A17 Pro chip or better. Besides the newly-released iPhone 16 range, which uses the new A18 chip, the only iPhones with Apple Intelligence are the iPhone 15 Pro and iPhone 15 Pro Max. The base iPhone 15 won’t get Apple Intelligence, because it uses the older A16 chipset.