Jet fighter generations classify the major technology leaps in the historical development of the jet fighter. Different authorities have identified different technology jumps as the key ones, dividing fighter development into different numbers of generations. Five generations are now widely recognised, with the development of a sixth under way.

In 1990, air historian Richard P. Hallion proposed a classification of jet fighters into six generations up to that time. These may be broadly described as subsonic, transonic, supersonic, Mach 2, multi-mission, and high-maneuverability. Other schemes comprising five generations up to around the same period have since been described, although the demarcation lines between generations differ. John W.R. Taylor and John F. Guilmartin (Encyclopedia Britannica) follow Hallion, except that they condense the last two into one. A NASA web publication divides jet development, up to 2004, into five stages; pioneer (straight wing), swept wing, transonic, the 1960s and 1970s on, culminating in types such as the F-15, F-16, and AV-8A.

In the 1990s, a different division came into use in Russia, in which a "fifth generation" fighter was proposed as a counter to the Lockheed Martin F-22 Raptor. In contrast, a preceding fourth generation filled in the gap since the F-15/16 era. This effectively condensed the previous classifications to three generations. In 2004, Aerospaceweb listed one such division into five generations. Although details differ, the basic classification into five generations has since been widely adopted.

The exact criteria for the various generation steps are not universally agreed on and are subject to some controversy. For example, Lockheed Martin has applied the term "fifth generation" to its F-22 and F-35 aircraft, but this has been challenged by its competitors Eurofighter GmbH and Boeing IDS. It has been suggested that Lockheed Martin "labeled the F-35 a 'fifth-generation' fighter in 2005, a term it borrowed from Russia in 2004 to describe the F-22". Some accounts have subdivided the 4th generation into 4 and 4.5, or 4+ and 4++.

The table below shows how some authors have divided up the generations, progressively since 1990.

Five generations are now commonly recognised, with the fifth representing the latest generation in service (as of 2018). Future types at an early stage of development are expected to have even further enhanced capabilities and have become known as a sixth generation. The rest of this article broadly follows the analysis of Baker.

The earliest jet fighters appeared during and after the last years of World War II. They were similar in most respects to their piston-engined contemporaries, having straight, effectively unswept wings and being of wood and/or light alloy construction. (The Me 262 had a lightly swept wing, but this was done principally to achieve balance, and the sweep was deliberately kept too little to have a significant aerodynamic effect.^{[citation needed]}) They had little or no avionics, with their primary armament being manually-controlled guns. The Heinkel He 162 and Gloster Meteor also saw wartime service, while types such as the de Havilland Vampire and Lockheed F-80 were still working up to operational service when the war ended.

The introduction of the swept wing allowed transonic speeds to be reached, but controllability was often limited at such speeds. These aircraft were typically aimed at the air-superiority interceptor role. Notable types which took part in the Korean War of 1950–1953 include the Soviet Mikoyan-Gurevich MiG-15 and the North American F-86 Sabre. The Hawker Hunter appeared too late for the war but was widely used and took part in several later ones.