iPhone OS 2 is the second major release of the iOS mobile operating system developed by Apple Inc., being the successor to iPhone OS 1. It was the first release of iOS to support third-party applications via the App Store. iPhone OS 2.2.1 was the final version of iPhone OS 2.
It was succeeded by iPhone OS 3 on June 17, 2009. iPhone OS 2.0 became available on July 11, 2008 with the release of the iPhone 3G. Devices running iPhone OS 1 are upgradable to this version.
This version of iOS introduces the App Store, making third-party applications available to the iPhone and iPod Touch. Prior to the public release of iPhone OS 2.0, Apple held a keynote event to announce the iPhone OS Software Development Kit ("SDK") to developers. Originally it was called 1.2.