The Convair B-36 "Peacemaker" is a strategic bomber built by Convair and operated by the United States Air Force (USAF) from 1949 to 1959. The B-36 is the largest mass-produced piston-engined aircraft ever built, although it was exceeded in span and weight by the one-off Hughes H-4 Hercules (commonly known as the Spruce Goose). It has the longest wingspan of any combat aircraft. The B-36 was capable of intercontinental flight without refueling.

Entering service in 1948, the B-36 was the primary nuclear weapons delivery vehicle of Strategic Air Command (SAC) until it was replaced by the jet-powered Boeing B-52 Stratofortress beginning in 1955. All but four aircraft have been scrapped.

The design of the B-36 can be traced to early 1941, prior to the entry of the United States into World War II. At the time, Britain was at risk of falling to the Nazi "Blitz" attacks, making strategic bombing attacks by the United States Army Air Corps (USAAC) against Germany impossible with the aircraft available.

The United States would need a new bomber to reach Europe and return to bases in North America, necessitating a combat range of at least 5,700 mi (9,200 km), the length of a Gander, Newfoundland–Berlin round trip. The USAAC therefore sought a bomber of truly intercontinental range. The German Reichsluftfahrtministerium (RLM) would request the similar ultralong-range Amerikabomber program on 12 May 1942.

The USAAC sent out an initial request on 11 April 1941, asking for a 450 mph (720 km/h) top speed, a 275 mph (443 km/h) cruising speed, a service ceiling of 45,000 ft (14,000 m) and a maximum range of 12,000 mi (19,000 km) at 25,000 ft (7,600 m). These requirements were too demanding and far exceeded the technology of the day, so on 19 August 1941, they were reduced, to a maximum range of 10,000 mi (16,000 km), an effective combat radius of 4,000 mi (6,400 km) with a 10,000 lb (4,500 kg) bomb-load, a cruising speed between 240 and 300 mph (390 and 480 km/h), and a service ceiling of 40,000 ft (12,000 m) The ceiling in both cases was chosen to exceed the maximum effective altitude of most of Nazi Germany's anti-aircraft guns.

In the Pacific, the USAAF needed a bomber capable of reaching Japan from bases in Hawaii, and the development of the B-36 became a priority. Secretary of War Henry L. Stimson, in discussions with high-ranking officers of the USAAF, decided to waive normal army procurement procedures. On 23 July 1943, 15 months after the Germans' Amerikabomber proposals, and the same day that the German firm Heinkel began design on a six-engined bomber of their own, the USAAF submitted a "letter of intent" to Convair for an initial production run of 100, even before testing of the two prototypes was complete. The first delivery was due in August 1945, and the last in October 1946, but Consolidated (by now renamed Convair after merging with Vultee Aircraft) delayed delivery. Three months after V-E Day the aircraft was unveiled on 20 August 1945, and flew for the first time on 8 August 1946.

After the start of the Cold War with the 1948 Berlin Airlift, and the 1949 atmospheric test of the first Soviet atomic bomb, American military planners sought bombers capable of delivering the very large and heavy first-generation atomic bombs.

The B-36 was the only American aircraft with the range and payload to carry such bombs from airfields on American soil to targets in the USSR. The modification to allow the use of larger atomic weapons on the B-36 was called the "Grand Slam Installation".