Forever known as the aircraft which dropped the world's only atomic bombs in combat, the Boeing B-29 Superfortress was by far the largest and most deadly bomber of World War II. It originated from a VLR (Very Long Range) bomber requirement of 1938 capable of dropping a 20,000 lb bomb load over three thousand miles. The long distances of the Pacific theater made such a bomber a necessity although various development problems caused the B-29 to become operational only until mid-1944 when it began flying from Chinese bases, once the Marianas Islands were secured they became the principal base of operations for the XX Bomber Command. High-flying bombing was the norm until the devastating 9/10 March 1945 raid on Tokyo proved the effectiveness of low-flying incendiary bombing (more people were killed in this raid than in either atomic bombing). Ultimately, B-29s from the 509th Composite Group were modified to become the world's first atomic bombers, leveling Hiroshima and Nagasaki and bringing World War II to an end. Unlike most wartime bombers, the B-29 found life after the war as the US's first strategic nuclear bomber: it saw considerable action during the Korean War and served in a variety of guises (including British and Soviet service) until finally retired in 1960.

The prototype XB-29 first flew on 21 September 1942 and production YB-29s and B-29s entered combat in 1944 as high-flying daylight bombers. B-29s were extremely advanced technologically: they were the first heavy bombers to feature a fully pressurized cabin and remote-controlled turrets. They were also radar-equipped. Other wartime variants included the B-29A with a different wing construction and the stripped-down B-29B (built by Bell) with fewer guns and lack of a computerized control system. B-29s continued for some years as the US's main strategic bombers, serving extensively in the Korean War also. A greatly improved post-war variant was the B-29D, later redesignated B-50A due to political reasons, with increased weights, more durable alloys, and a larger fin and rudder. Variants of this ostentibly new aircraft included the B-50B with even greater weights and the B-50D with redesigned nose glazing and provision for external fuel tanks and aerial refuelling (other variants were the RB-50B photo-recon platform and KB50-J and -K tankers). Finally, a number of loaned B-29s were flown by the RAF as the Washington B.1 while a reverse-engineered Soviet version was designated Tu-4 and is covered separately.