The Douglas C-47 Skytrain or Dakota (RAF designation) is a military transport aircraft that was developed from the civilian Douglas DC-3 airliner. It was used extensively by the Allies during World War II. During the war the C-47 was used for troop transport, cargo, paratrooper drops, glider towing, and military cargo parachute drops. The C-47 remained in front-line service with various military operators for many years. It was produced in approximately triple the numbers as the larger, much heavier payload Curtiss C-46 Commando, which filled a similar role for the U.S. military.

Approximately 100 countries' armed forces have operated the C-47 with over 60 variants of the aircraft produced. As with the civilian DC-3, the C-47 remains in service, over 80 years after the type's introduction.

The C-47 differed from the civilian DC-3 by way of numerous modifications, including being fitted with a cargo door, hoist attachment and strengthened floor - along with a shortened tail cone for glider-towing shackles, and an astrodome in the cabin roof.

During World War II, the armed forces of many countries used the C-47 and modified DC-3s for the transport of troops, cargo, and wounded. The U.S. naval designation was R4D. More than 10,000 aircraft were produced in Long Beach and Santa Monica, California, and Oklahoma City, Oklahoma. Between March 1943 and August 1945, the Oklahoma City plant produced 5,354 C-47s.

The specialized C-53 Skytrooper troop transport started production in October 1941 at Douglas Aircraft's Santa Monica plant. It lacked the cargo door, hoist attachment, and reinforced floor of the C-47. Only 380 aircraft were produced in all because the C-47 was found to be more versatile.

Large numbers of DC-3s and surplus C-47s were in commercial use in the United States in the 1940s. In response to proposed changes to the Civil Air Regulations airworthiness requirements that would limit the continuing use of these aircraft, Douglas offered a late-1940s DC-3 conversion to improve takeoff and single-engine performance. This new model, the DC-3S or "Super DC-3", was 39 in (0.99 m) longer. It allowed 30 passengers to be carried, with increased speed to compete with newer airliners. The rearward shift in the center of gravity led to larger tail surfaces and new outer, swept-back wings. More powerful engines were installed along with shorter, jet ejection-type exhaust stacks. These were either 1,475 hp (1,100 kW) Wright R-1820 Cyclones or 1,450 hp (1,081 kW) Pratt & Whitney R-2000 Twin Wasps in larger engine nacelles. Minor changes included wheel-well doors, a partially retractable tailwheel, flush rivets, and low-drag antenna. These all contributed to an increased top speed of 250 mph (400 km/h; 220 kn). With over 75% of the original DC-3/C-47 configuration changed, the modified design was virtually a new aircraft. The first DC-3S made its maiden flight on 23 June 1949.

The changes fully met the new FAR 4B airworthiness requirements, with significantly improved performance. However, little interest was expressed by commercial operators in the DC-3S. It was too expensive for the smaller operators that were its main target; only three were sold to Capital Airlines. The U.S. Navy and U.S. Marine Corps had 100 of their R4D aircraft modified to Super DC-3 standards as the R4D-8, later redesignated the C-117D.

The C-47 was vital to the success of many Allied campaigns, in particular, those at Guadalcanal and in the jungles of New Guinea and Burma, where the C-47 and its naval version, the R4D, made it possible for Allied troops to counter the mobility of the light-traveling Japanese Army. C-47s were used to airlift supplies to the encircled American forces during the Battle of Bastogne in Belgium. Possibly its most influential role in military aviation, however, was flying "The Hump" from India into China. The expertise gained flying "The Hump" was later used in the Berlin Airlift, in which the C-47 played a major role until the aircraft were replaced by Douglas C-54 Skymasters.^{[citation needed]}