The trombone is a musical instrument in the brass family. Like all brass instruments, sound is produced when the player’s vibrating lips (embouchure) cause the air column inside the instrument to vibrate. The trombone is usually characterised by a telescopic slide with which the player varies the length of the tube to change pitches, although the valve trombone uses three valves similar to those on a trumpet.

The word trombone derives from Italian tromba (trumpet) and -one (a suffix meaning "large"), so the name literally means "large trumpet". Trombones and trumpets share the important characteristic of having predominantly cylindrical bores. Therefore, the most frequently encountered trombones—the tenor and bass trombone—are the tenor and bass counterparts of the trumpet. They are both pitched in B♭—with the slide all the way in, the notes of the harmonic series based on B♭ can be played—but trombones generally read music in concert pitch.