A brass instrument which is usually pitched in B flat (and occasionally C). It resembles a trumpet, and the tube has the same length but a wider, conical bore. It was developed in Germany from a traditional English valveless bugle, with the first version sold in Berlin in 1828. The valved bugle provided Adolphe Sax (creator of the saxophone family) with the inspiration for his B flat soprano (contralto) saxhorns, on which the modern-day flugelhorn is modelled.

The flugelhorn is built in the same B flat pitch as many trumpets and cornets. It usually has 3 piston valves and employs the same fingering system as other brass instruments, but 4-piston valve and rotary valve variants also exist. It can thus be played without too much trouble by trumpet and cornet players, although some adaptation of playing style may be needed. It is usually played with a more deeply conical mouthpiece than either trumpets or cornets (although not as conical as that of a French horn). 

Some modern flugelhorns feature a fourth valve that lowers the pitch a perfect fourth (similar to the fourth valve on some euphoniums, tubas and piccolo trumpets, or the trigger on trombones). This adds a useful low range that, coupled with the flugelhorn's dark sound, extends the instrument's abilities.

The tone of the flugelhorn is fatter and usually regarded as more mellow and dark than the trumpet or cornet. Its sound has been described as halfway between a trumpet and a French horn, whereas the cornet is halfway between a trumpet and a flugelhorn. The flugelhorn is not generally used for aggressive or bright displays as trumpets and cornets often are, but tends more towards a softer and more reflective role.

The flugelhorn is a standard member of the British-style brass band, and is also used frequently in jazz and appears occasionally in orchestral and concert band music.