The Airbus A350 is a long-range, wide-body twin-engine airliner developed and produced by Airbus. The initial A350 design proposed in 2004, in response to the Boeing 787 Dreamliner, would have been a development of the Airbus A330 with composite wings, advanced winglets, and new efficient engines. Due to inadequate market support, Airbus switched in 2006 to a clean-sheet extra wide body (XWB) design, powered by two Rolls-Royce Trent XWB high bypass turbofan engines. The prototype first flew on 14 June 2013 from Toulouse, France. Type certification from the European Aviation Safety Agency (EASA) was obtained in September 2014, followed by certification from the Federal Aviation Administration (FAA) two months later.

The A350 is the first Airbus aircraft largely made of carbon-fibre-reinforced polymers. The fuselage is designed around a 3-3-3 nine-across economy cross-section, an increase from the eight-across A330/A340 2-4-2 configuration. (The A350 has 3-4-3 ten-across economy seating on select aircraft.) It has a common type rating with the A330. The airliner has two variants: the A350-900 typically carries 300 to 350 passengers over a 15,750-kilometre (8,500-nautical-mile) range, and has a 283-tonne (624,000 lb) maximum takeoff weight (MTOW); the longer A350-1000 accommodates 350 to 410 passengers and has a maximum range of 16,700 kilometres (9,000 nmi) and a 322-tonne (710,000 lb) MTOW.

On 15 January 2015, the first A350-900 entered service with Qatar Airways, followed by the A350-1000 on 24 February 2018 with the same launch operator. As of September 2025^[update], Singapore Airlines is the largest operator with 65 aircraft in its fleet, while Turkish Airlines is the largest customer with 110 aircraft on order. A total of 1,445 A350 family aircraft have been ordered and 675 delivered, of which 674 aircraft are in service with 38 operators. The global A350 fleet has completed more than 1.58 million flights on more than 1,240 routes, transporting more than 400 million passengers with no fatalities and one hull loss in an airport-safety-related incident. It succeeds the A340 and competes against Boeing's large long-haul twinjets, the Boeing 777, its future successor, the 777X, and the 787 Dreamliner.

Airbus initially rejected Boeing's claim that the Boeing 787 Dreamliner would be a serious threat to the Airbus A330, stating that the 787 was just a reaction to the A330 and that no response was needed. When airlines urged Airbus to provide a competitor, Airbus initially proposed the "A330-200 Lite", a derivative of the A330 featuring improved aerodynamics and engines similar to those on the 787. The company planned to announce this version at the 2004 Farnborough Airshow, but did not proceed.

On 16 September 2004, Airbus president and chief executive officer Noël Forgeard confirmed the consideration of a new project during a private meeting with prospective customers. Forgeard did not give a project name, and did not state whether it would be an entirely new design or a modification of an existing product. Airline dissatisfaction with this proposal motivated Airbus to commit €4 billion to a new airliner design.

On 10 December 2004, Airbus' shareholders, EADS and BAE Systems, approved the "authorisation to offer" for the A350, expecting a 2010 service entry. Airbus then expected to win more than half of the 250-300-seat aircraft market, estimated at 3,100 aircraft overall over 20 years. Based on the A330, the 245-seat A350-800 was to fly over a 8,600 nmi (15,900 km; 9,900 mi) range and the 285-seat A350-900 over a 13,900 km (7,500 nmi; 8,600 mi) range. Fuel efficiency would improve by over 10% with a mostly carbon fibre reinforced polymer wing and initial General Electric GEnx-72A1 engines, before offering a choice of powerplant. It had a common fuselage cross-section with the A330 and also a new horizontal stabiliser.

On 13 June 2005 at the Paris Air Show, Middle Eastern carrier Qatar Airways announced that they had placed an order for 60 A350s. In September 2006 the airline signed a memorandum of understanding with General Electric (GE) to launch the GEnx-1A-72 engine for the new airliner model. Emirates sought a more improved design and decided against ordering the initial version of the A350.

On 6 October 2005, the programme's industrial launch was announced with an estimated development cost of around €3.5 billion. The A350 was initially planned to be a 250 to 300-seat twin-engine wide-body aircraft derived from the existing A330's design. Under this plan, the A350 would have modified wings and new engines while sharing the A330's fuselage cross-section. For this design, the fuselage was to consist primarily of aluminium-lithium rather than the carbon-fibre-reinforced polymer (CFRP) fuselage on the Boeing 787. The A350 would see entry in two versions: the A350-800 with a 8,800 nmi (16,300 km; 10,100 mi) range with a typical passenger capacity of 253 in a three-class configuration, and the A350-900 with 7,500 nmi (13,900 km; 8,600 mi) range and a 300-seat three-class configuration. The A350 was designed to be a direct competitor to the Boeing 787-9 and 777-200ER.