Euphonium (from the Greek word εὔφωνος, meaning "well-sounding" or "sweet-voiced") is a conical-bore, baritone-voiced brass instrument. The euphonium is a valved instrument; nearly all current models are piston valved, though rotary valved models do exist.
A person who plays the euphonium is sometimes called a euphoniumist, euphophonist, or a euphonist, while British players often colloquially refer to themselves as euphists, or euphologists. Similarly, the instrument itself is often referred to as eupho or euph.
Visually, the euphonium has a similar appearance to its better known cousin, the tuba, the difference being the former is slightly smaller and has a slightly higher pitch than the latter.