iPhone OS 3 is the third major release of what is now iOS, released on June 17, 2009, two days ahead of the iPhone 3GS. It was the platform's great catching-up release: copy and paste — the omission that had headlined two years of criticism — finally arrived, implemented with the tap-and-drag selection handles still in use today, alongside MMS, Spotlight search, landscape keyboards across core apps, and push notifications for third-party apps, the stopgap for the multitasking the hardware couldn't yet afford.

It was also the last release to carry the "iPhone OS" name — and the first to run on an iPad: the tablet launched in April 2010 on the 3.2 branch, whose iPad-only interface conventions previewed the split that eventually became iPadOS.

The 100-plus additions ran deep: cut/copy/paste with the magnification loupe, MMS (carrier permitting — AT&T delayed it months in the US), system-wide Spotlight, voice memos, a Find My iPhone service via MobileMe, in-app purchases, peer-to-peer Bluetooth gaming, tethering (again, carrier permitting), and the Voice Control that shipped with the 3GS. Point release 3.1 added Genius app recommendations; 3.2 was the iPad's launch branch with popovers, split views, and the tablet home screen.

iPhone 3GS, iPhone 3G, the original iPhone, all three iPod touch generations (paid upgrade for the older two), and the original iPad (3.2 branch). 3.1.3 was the final release for the original iPhone and first-generation iPod touch — ending the 2007 hardware's software life at two and a half years.

iPhone OS 3 completed the platform's feature parity with the smartphones it had disrupted, and its unglamorous additions — selection handles, Spotlight, push notifications, in-app purchases — became permanent infrastructure. The in-app purchase API in particular reshaped the App Store's economics toward the freemium model that dominates it still. With the iPad's 3.2 branch it also began the platform's multi-device era, setting up the rename that followed: iOS 4.