A triplane is a fixed-wing aircraft equipped with three sets of wings, each roughly the same size and mounted one above the other. Traditionally, the vertical wings, elevators, and canards are not included in this count. Typically, the lower set of wings would be level with the underside of the aircraft's fuselage, the middle set level with the top of the fuselage, and the top set supported above the fuselage on struts. The first triplane was designed in 1908 by Ambroise Goupy and built by Blériot, flown with a 37 kW (50 hp) Renault engine. The British aviation pioneer A.V. Roe built several experimental triplane designs before turning to the tractor biplane. Triplanes have greater wing area than biplanes and monoplanes of similar wing span and chord, potentially offering increased lift and tighter turning radii.
During World War I, some aircraft manufacturers turned to this configuration in an effort to gain extra maneuverability for fighter aircraft, at a penalty of greater drag and therefore lower speed. In practice, triplanes generally offered inferior performance to biplanes, and only a few aircraft of this configuration reached production status. Triplane layouts were also experimented with on large aircraft such as early heavy bombers such as the Witteman-Lewis XNBL-1 Barling Bomber and on some experimental British anti-zeppelin fighters.
The Sopwith Triplane was the first triplane to see service during World War I, but the best-known triplane of that conflict is the Fokker Dr.I, immortalised as the aircraft most closely identified with Manfred von Richthofen, the "Red Baron".
Recently, the term "tandem triplane" has been used for recent jet fighter aircraft that have canards in addition to normal flying surfaces (main wings and horizontal tailplanes) for increased maneuverablility and/or increased lift for short takeoffs or landings. These are generally not considered triplanes in the traditional sense. Examples of these include the Sukhoi Su-33, Su-37, Su-47, the Mikoyan Mig-33, and NASA's F-15S/MTD aircraft and related programs. A handful of civil aircraft also share the tandem triplane layout, such as the Piaggio P180 Avanti and the Peterson 260SE; the latter being a STOL conversion of the Cessna 182.
While triplane designs are already relatively uncommon, aircraft with four or more sets of wings are even rarer. Extreme examples include multiplanes designed by Horatio Phillips, one of which had two hundred sets of wings. Another example is the Caproni Ca.60, a one-off transatlantic seaplane, which had three sets of triplane wings taken from Caproni Ca.4 bombers. There was also the tetra-winged (four-winged) Supermarine Nighthawk, designed to shoot down zeppelins, that never entered production.