Those who use an iPad 2 or later, or an iPhone 4 or later, will be able to run the new operating system. iPad mini users can also download the new-look iOS 7.
It features an entirely new colour palette, redesigned applications and new ringtones and features.
iOS 7 is completely free to download and can be obtained from today (September 18) via either iTunes or the software update section of the iPhone's settings menu.
Meanwhile, Apple's new iPhone 5S and 5C will go on sale in nine countries, including the US and UK, this Friday (September 20).