The Power Macintosh G4 (Power Mac G4) was series of personal computers made by Apple. It used the PowerPC G4 (PPC7400) series of microprocessors.

The original Power Macintosh G4 was introduced at the Seybold conference in San Francisco on 31 August 1999. The early 350MHz and 400MHz versions were essentially Power Macintosh G3 Blue & White computers in a "graphite" colored case and with the new CPU, while the higher-speed models used an all-new motherboard design with AGP graphics. Shortly thereafter, the entire G4 line was updated to the AGP motherboard. The 500MHz version began shipping on 16 February 2000 due to shortages of the highest speed CPU. The design was updated at the Macworld Expo New York on July 19 2000 and now included dual processor 450MHz and 500MHz versions. It was also the first personal computer to include gigabit ethernet. The same design was later updated on 9 January 2001 and was the first personal computer to include a built-in DVD-R drive. The Models were offered in 466MHz, 533MHz, 667MHz, 733MHz and dual 533MHz configurations.

The second generation of G4s was introduced at the Macworld Expo New York on 18 July 2001. It had a redesigned case and was offered in 733MHz, 867MHz and the dual 800MHz configurations. The design was updated on 28 January 2002 with the first Mac to break the 1GHz barrier. The models were offered in 800MHz, 933MHz and dual 1GHz configurations.

The third generation of G4s was introduced on 13 August 2002 and featured new case design once again. The case also had four air intake holes on the front. All models were sold in dual processor configurations running at 867MHz, 1GHz or 1.25GHz. The models were known for their noisiness. The design was updated in 28 January 2003 to a top speed of 1.42GHz. The models had an option for integrated Bluetooth and also had a Firewire 800 connector built-in. These were also the first Power Mac incapable of booting Mac OS 9. On 23 June 2003, Apple quietly re-introduced a Mac OS 9 compatible Power Mac G4 simultaneously with the Power Mac G5 because of high demand for Mac OS 9 machines. It was in essence the August 2002 model re-released. It was discontinued on 9 June 2004.