The Lockheed Martin F-35 Lightning II is a family of single-seat, single-engine, fifth generation multirole fighters under development to perform ground attack, reconnaissance, and air defense missions with stealth capability. The F-35 has three main models; the F-35A is a conventional takeoff and landing variant, the F-35B is a short take off and vertical-landing variant, and the F-35C is a carrier-based variant.

The F-35 is descended from the X-35, the product of the Joint Strike Fighter (JSF) program. JSF development is being principally funded by the United States, with the United Kingdom and other partner governments providing additional funding. The partner nations are either NATO members or close U.S. allies. It is being designed and built by an aerospace industry team led by Lockheed Martin. The F-35 took its first flight on 15 December 2006.

The United States intends to buy a total of 2,443 aircraft to provide the bulk of its tactical airpower for the US Air Force, Marine Corps and Navy over the coming decades. The United Kingdom, Australia, Italy, Canada, Netherlands, Norway, Turkey, Israel, and Japan all will equip their air and/or naval forces with the F-35, although Japan has warned that it may halt their purchase if the unit costs increase, and Canada has indicated it is not fully committed to purchasing the aircraft. The United States is projected to spend an estimated US$323 billion for development and procurement on the F-35 program, making it the most expensive defense program ever. The total lifecycle cost for the entire American fleet is estimated to be US$1.51 trillion over its 50-year life, or $618 million per plane. Testifying before a Canadian parliamentary committee in 2011, Rear Admiral Arne Røksund of Norway estimated that his country's 52 F-35 fighter jets will cost $769 million each over their operational lifetime.

In a current military parlance, a strike fighter is a multirole combat aircraft designed to operate primarily in the air-to-surface attack role while also incorporating certain performance characteristics of a fighter aircraft. As a category, it is distinct from fighter-bombers. Examples of contemporary American strike fighters are the McDonnell Douglas F-15E Strike Eagle, Boeing F/A-18E/F Super Hornet, and Lockheed Martin F-35 Lightning II.

Since 1940s, the term "strike fighter" was occasionally used in the navies to refer to fighter aircraft capable of performing air-to-surface strikes, such as the Westland Wyvern and Blackburn Firebrand. It became normally used in the United States Navy at the end of 1970s, being the official description of the new McDonnell Douglas F/A-18 Hornet. In 1983, the U.S. Navy even renamed each existing Fighter Attack Squadron to Strike Fighter Squadron to emphasize the air-to-surface mission (as the "Fighter Attack" designation was confused with the "Fighter" flying pure air-to-air missions).