Interflug GmbH (German: INTERFLUG Gesellschaft für internationalen Flugverkehr m.b.H.; [ˈɪntɐfluːk]) was the national airline of East Germany (officially the “German Democratic Republic”) from 1963 to 1991. Based in East Berlin, it operated scheduled and chartered flights to European and intercontinental destinations out of its hub at Berlin Schönefeld Airport, focusing on Comecon countries. Interflug also had significant crop dusting operations. Following German reunification, the company was liquidated.

Until 1945, Deutsche Luft Hansa had served as German flag carrier. Following the end of World War II and the subsequent allied occupation of Germany, all aircraft in the country were seized and the airline was liquidated. In 1954, a West German company acquired the Lufthansa trademark. In 1955, Deutsche Lufthansa was founded as a rival East German flag carrier. It soon became obvious that the East German airline would likely lose a lawsuit over the use of the Lufthansa branding. As a result, Interflug was set up on 18 September 1958 as a "backup" company, initially intended to complement the East German aviation industry by operating chartered flights. In 1963, the East German Lufthansa was liquidated, officially due to poor profitability (though this step foreclosed the imminent stripping of the Lufthansa name). Its staff, aircraft fleet, and route network were transferred to Interflug, which henceforth served as the East German flag carrier.

As a state-owned airline, Interflug and its approximately 8,000 employees were under the control of the National Defense Council, in supreme command of the East German armed forces. The majority of Interflug pilots were reserve officers of the National People's Army (and as such were required to be members of the Socialist Unity Party), and its aircraft could be requisitioned for military purposes at any time. Klaus Henkes, who became General Director of the airline in 1978, had previously served as General of the East German Air Force. Applicants for flight attendant jobs had to be approved of by the Stasi, which assessed their political reliability, in an attempt to minimize espionage and defection to Western countries. Interflug crews who associated with employees of airlines from non-socialist countries risked suspension. Each flight crew was assigned a political officer who gave political lectures during flights.

The airline's route network and fleet of Soviet-built aircraft grew significantly in the 1960s. The Ilyushin Il-18 turboprop airliner became the workhorse of Interflug's short-haul flights during that period. The company had been the intended primary operator of the Baade 152, an early jet airliner constructed in East Germany. Its development never went beyond the prototype phase and was abandoned in 1961. In 1969, the Tupolev Tu-134 was introduced, the first jet airliner operated by Interflug, used on European routes. The long-range Il-62 joined the fleet in 1971. That same year, the number of Interflug passengers reached 1 million. At its peak, Interflug flew to destinations such as Havana, Cuba, Singapore and Conakry, Guinea.

As a result of the 1970s energy crisis and increasing fuel prices, Interflug gradually dismantled its domestic route network. The last scheduled domestic flight, to transport prisoners from East Berlin to Erfurt, took place in April 1980.

During the 1980s, Interflug's aging fleet caused increasing difficulties: fuel efficiency was inferior to that of contemporary western airliners, and noise pollution regulations meant the airline had to pay higher landing fees and was even banned from operating at some airports. With some exceptions, Western-built airliners (most notably those produced by Boeing, McDonnell Douglas, and Airbus) could not be delivered to Soviet bloc countries because of the CoCom embargo. Following a deal between Boeing and LOT Polish Airlines for the purchase of six Boeing 767 aircraft, and in order to acknowledge the Perestroika movement, commercial airliners were exempted from the trade embargo in 1988. Malév Hungarian Airlines also bought Boeing aircraft in 1988, and later that year, Interflug placed an order for three Airbus A310 long-haul aircraft, worth DM 420 million. The deal was secured with the support of Franz Josef Strauss, then Minister-President of Bavaria, chairman of the Airbus supervisory board and responsible for West German loans to East Germany.

The first Airbus A310 was delivered to Interflug on 26 June 1989. The East German crews for the new aircraft type were trained in West Germany; aircraft maintenance was also performed there. The A310 enabled non-stop flights to Cuba (flights had previously required a fuel stop at Gander International Airport in Canada).

Following the fall of the Berlin Wall on 9 November 1989 and the subsequent political upheaval in East Germany, several airlines expressed interest in buying parts of the highly unprofitable company to secure a share of the German air traffic market, especially in Berlin. In early March 1990, Lufthansa signed a letter of intent to acquire 26 percent of Interflug, but the offer was blocked by Germany's Federal Cartel Office. Plans for a takeover by British Airways did not materialize either (the UK airline instead founded Deutsche BA in 1992). On 1 July 1990, Interflug became a member of the International Air Transport Association (IATA).