A wide-body aircraft, also known as a twin-aisle aircraft, is an airliner with a fuselage wide enough to accommodate two passenger aisles with seven or more seats abreast. The typical fuselage diameter is 5 to 6 m (16 to 20 ft). In the typical wide-body economy cabin, passengers are seated seven to ten abreast, allowing a total capacity of 200 to 850 passengers. The largest wide-body aircraft are over 6 m (20 ft) wide, and can accommodate up to eleven passengers abreast in high-density configurations.

By comparison, a typical narrow-body airliner has a diameter of 3 to 4 m (10 to 13 ft), with a single aisle, and seats between two and six people abreast.

Wide-body aircraft were originally designed for a combination of efficiency and passenger comfort and to increase the amount of cargo space. However, airlines quickly gave in to economic factors, and reduced the extra passenger space in order to insert more seats and increase revenue and profits.

Wide-body aircraft are also used for the transport of commercial freight and cargo and other special uses, described further below.

The term jumbo jet usually refers to the largest variants of wide-body airliners; examples include the Boeing 747 (the first wide-body and original "jumbo jet"), Airbus A380 ("superjumbo jet"), Boeing 777X and Boeing 777 ("mini jumbo jet"). The phrase "jumbo jet" derives from Jumbo, a circus elephant in the 19th century.

Seven-abreast aircraft typically seat 160 to 260 passengers, eight-abreast 250 to 380, nine- and ten-abreast 350 to 480.

By the end of 2017, nearly 8,800 wide-body airplanes had been delivered since 1969, production peaking at 412 per year in 2015.