The flugelhorn (also spelled fluegelhorn or flügelhorn) is a brass instrument resembling a trumpet but with a wider, conical bore. It is thought by some to be a member of the saxhorn family developed by Adolphe Sax (who also developed the saxophone); however, other historians assert that it has been derived from the keyed bugle by Michael Saurle (father), Munich 1832 (Royal Bavarian privilege for a "chromatic Flügelhorn" 1832), thus predating Adolphe Sax's innovative work [1].

The original German spelling of Flügelhorn translates into English as wing horn. One possible etymology is that the instrument was used on the battlefield to summon the flanks, or wings, of an army into battle [2].

The flugelhorn is built in the same B-flat pitch as many trumpets and cornets. It usually has three piston valves and employs the same fingering system as other brass instruments. Four valve and rotary valve variants also exist. It can thus be played without too much trouble by trumpet and cornet players, though some adaptation may be needed to their playing style. It is usually played with a more deeply conical mouthpiece than either trumpets or cornets (though not as conical as that on a horn).

The tone is fatter and usually regarded as more "mellow" and "dark" than that of the trumpet or cornet. It has a similar level of agility to the cornet but is more difficult to control in the high register where in general it "slots" or locks on to notes less easily. It is not generally used for aggressive or bright displays as both trumpet and cornet can be, but tends more towards a softer and more reflective role. Its main areas of use are in jazz and in the brass band, though it does get occasional use in orchestral writing. The flugelhorn is the melody-instrument of a fanfare-orchestra.

Flugelhorns have occasionally been used as the alto or low soprano voice in a drum and bugle corps. However this is increasingly rare, as the mellophone, with its larger bell, is more often picked to mimic the sound of a French horn.

Miles Davis was a pioneer in the use of the flugelhorn in jazz on the albums Miles Ahead and Sketches of Spain, both of which were arranged by Gil Evans, although he did not use it much on later projects. Other prominent jazz flugelhorn players include Boban Markovic, Clark Terry, Freddie Hubbard, Art Farmer, Hugh Masekela, Tony Guerrero, Jimmy Owens, Chet Baker, Chuck Mangione, Woody Shaw and Tom Harrell.

Some modern flugelhorns are built with a fourth valve which takes them down in pitch a perfect fourth (similar to the fourth valve sometimes found on euphoniums and tubas as well as the trigger on trombones), adding a useful area of low range which when coupled with the dark sound gives an interesting extension to the instrument's abilities. More often, however, the fourth valve is used in place of the first and third valve combination, which is somewhat sharp (and which is flattened on trumpets and cornets and some three-valve flugelhorns by a "kicker" slide on the first and/or third valve).