The iPhone 5 is a smartphone that was developed and marketed by Apple Inc. It is the 6th generation iPhone, succeeding the iPhone 4s, and preceding both the iPhone 5s and iPhone 5c. It was formally unveiled as part of a press event on September 12, 2012, and subsequently released on September 21, 2012. The iPhone 5 was the first iPhone to be announced in September, and setting a trend for subsequent iPhone releases, the first iPhone to be completely developed under the guidance of Tim Cook and the last iPhone to be overseen by Steve Jobs. The iPhone 5's design was used three times, first with the iPhone 5 itself in 2012, then with the iPhone 5s in 2013, and finally with the first-generation iPhone SE in 2016.

The iPhone 5 featured major design changes in comparison to its predecessor. These included an aluminum-based body which was thinner and lighter than previous models, a taller 4-inch screen with a nearly 16:9 aspect ratio, the Apple A6 system-on-chip, LTE support, and Lightning, a new compact dock connector which replaced the 30-pin design used by previous iPhone models. This was the second iPhone after the iPhone 4s to include Apple's new Sony-made 8 MP camera.

Apple began taking pre-orders on September 14, 2012, and over two million were received within 24 hours. Initial demand for the iPhone 5 exceeded the supply available at launch on September 21, 2012, and was described by Apple as "extraordinary", with pre-orders having sold twenty times faster than its predecessors. While reception to the iPhone 5 was generally positive, consumers and reviewers noted hardware issues, such as an unintended purple hue in photos taken, and the phone's coating being prone to chipping. Reception was also mixed over Apple's decision to switch to a different dock connector design, as the change affected iPhone 5's compatibility with accessories that were otherwise compatible with previous iterations of the line.

Alongside the iPhone 4, the iPhone 5 was officially discontinued by Apple on September 10, 2013, with the announcement of its successors, the iPhone 5s and the iPhone 5c. The iPhone 5 has the joint second-shortest lifespan of any iPhone ever produced with only twelve months in production, breaking with Apple's standard practice of selling an existing iPhone model at a reduced price upon the release of a new model. This was broken by the iPhone X which only had ten-months in production from November 2017 to September 2018, and tied with the iPhone XS which had twelve-months from September 2018 to September 2019. The iPhone 11 Pro and subsequent "Pro" designated iPhones have also had twelve month availability, being discontinued upon release of its successor.

The iPhone 5 was replaced as a midrange and then an entry-level device by the iPhone 5c; the 5c internal hardware specifications are almost identical to the 5 albeit having a less expensive polycarbonate exterior shell. The iPhone 5 supports iOS 6, 7, 8, 9 and 10. The iPhone 5 does not support iOS 11 due to it dropping support for 32-bit devices. The iPhone 5 is the second iPhone to support five major versions of iOS after the iPhone 4s.