The iPhone 4 is a smartphone that was designed, developed, and marketed by Apple Inc. It is the fourth generation of the iPhone lineup, succeeding the iPhone 3GS and preceding the 4S. Following a number of notable leaks, the iPhone 4 was first unveiled on June 7, 2010, at Apple's Worldwide Developers Conference in San Francisco, and was released on June 24, 2010, in the United States, United Kingdom, France, Germany, and Japan. The iPhone 4 introduced a new hardware design to the iPhone family, which Apple's CEO Steve Jobs touted as the thinnest smartphone in the world at the time; it consisted of a stainless steel frame which doubled as an antenna, with internal components situated between two panels of aluminosilicate glass. The iPhone 4 introduced Apple's new high-resolution "Retina Display", while maintaining the same physical size and aspect ratio as its precursors, Apple's A4 system-on-chip, along with iOS 4—which notably introduced multitasking functionality and app folders. It was the first iPhone at the time to include a front-facing camera, which made possible Apple's new FaceTime video chat service, and the first to be released in a version for CDMA networks, ending AT&T's period as the exclusive carrier of iPhone products in the United States.

Apple Inc. is an American multinational corporation and technology company headquartered in Cupertino, California, in Silicon Valley. It designs, develops, and sells consumer electronics, computer software, and online services. Devices include the iPhone, iPad, Mac, Apple Watch, Vision Pro, and Apple TV; operating systems include iOS, iPadOS, and macOS; and software applications and services include iTunes, iCloud, Apple Music, and Apple TV+.