The McDonnell Douglas AV-8B Harrier II is a family of second-generation vertical/short takeoff and landing jet multirole aircraft of the late 20th century. Developed from the earlier Hawker Siddeley Harriers, it is primarily used for light attack or multi-role tasks, typically operated from small aircraft carriers. Versions are used by several NATO countries, including the United Kingdom, Spain, Italy, and the United States. Though it shares the designation letter number with the earlier AV-8A Harrier, the AV-8B Harrier II was extensively redesigned by McDonnell Douglas. Both models are commonly referred to as the Harrier Jump-jet.

The AV8B had its direct origins in a joint British-US project (Hawker-Siddeley and McDonnell Douglas) for a much-improved Harrier aircraft, the AV-16. However the British later pulled out of the program. Using things learned from AV-16 development, McDonnell continued the development work which lead to the AV-8B for the US Marine Corps. The aircraft was centered on the Marines' need for a light ground attack airplane and focused on payload and range as opposed to speed.

The first Harrier IIs produced were commonly known as the Day Attack variant, and are no longer in service. Most were upgraded to Night Attack Harrier or Harrier II Plus standards, with the remainder being withdrawn from service. Several variants of the Harrier are used by four countries' military forces: the United Kingdom, the United States, Spain and Italy. The US Marine Corps has operated the AV-8B since 1985.