The French horn is a valved brass wind instrument with a circular shape, tapering from a narrow mouthpiece to a flaring bell at the other end and producing a mellow tone. Often played with the right hand inside the bell, it is said to be the most difficult instrument to play. It is referred to in most countries without any nationalistic reference and is known as the "French" horn only in English-speaking countries.

The invention of valves in the early 19th century revolutionized the horn, allowing the player to alter the length of the tubing by the motion of a finger. Modern players use hand stopping to affect intonation and tone color. Composers from Bach, Beethoven, Strauss and Tchaikovsky to Bernstein and Gershwin have all written for the French horn. Most orchestras today include four horns. They are also used in concert and marching bands and brass ensembles.