Gun fu, a portmanteau of gun and kung fu (also known as gun kata, bullet ballet, gymnastic gunplay or bullet arts), is a style of sophisticated close-quarters gunfight resembling a martial arts combat that combines firearms with hand-to-hand combat and traditional melee weapons in an approximately 50/50 ratio. It can be seen in Hong Kong action cinema, and in American action films influenced by it.

The focus of gun fu is both artistic style and the usage of firearms in ways that they were not designed to be used. Shooting a gun from each hand (usually paired with jumping to the side at the same time), dual wielding, shots from behind the back, as well as the use of guns as melee weapons (usually knife fights) are all common. Other moves can involve submachine guns, assault rifles, combat shotguns, rocket launchers, and just about anything else that can be worked into a cinematic shot. It is often mixed with grappling maneuvers.

Gun fu has become a staple of modern action films due to its visual spectacle, a result of often impressive choreography and stuntwork, regardless of its unrealistic elements when compared to real-life gun warfare.

As the name suggests, gun fu has roots in martial arts films from Hong Kong action cinema, including wuxia films and kung fu films from the likes of Bruce Lee and Jackie Chan. These films typically involved martial artists fighting large numbers of enemies in stylized choreographed action set-pieces, with a fighting style that lay somewhere between brawling and dancing. Hong Kong filmmaker John Woo, who began his career directing martial arts films, took the martial arts style of action and added guns, combining the elegance and precision of kung fu with the brutality and violence of gangster films.

John Woo originated the style that would later be called gun fu in the 1986 Hong Kong action film A Better Tomorrow. The film launched the "heroic bloodshed" genre in Hong Kong, and gun fu action sequences became a regular feature in many of the subsequent heroic bloodshed films, which combined the elegance and precision of kung fu with the brutality and violence of gangster movies. John Woo continued to make several classic heroic bloodshed films, all featuring gun fu, and all starring leading man Chow Yun-fat.

Anthony Leong wrote of the gunfights in A Better Tomorrow,

Before 1986, Hong Kong cinema was firmly rooted in two genres: the martial arts film and the comedy. Gunplay was not terribly popular because audiences had considered it boring, compared to fancy kung fu moves or graceful swordplay of wuxia epics. What moviegoers needed was a new way to present gunplay—to show it as a skill that could be honed, integrating the acrobatics and grace of the traditional martial arts. And that's exactly what John Woo did. Using all of the visual techniques available to him (tracking shots, dolly-ins, slo-mo), Woo created beautifully surrealistic action sequences that were a 'guilty pleasure' to watch. There is also intimacy found in the gunplay—typically, his protagonists and antagonists will have a profound understanding of one another and will meet face-to-face, in a tense Mexican standoff where they each point their weapons at one another and trade words.

Stephen Hunter, writing in The Washington Post wrote,