A lute ( or ) is any plucked string instrument with a neck and a deep round back enclosing a hollow cavity, usually with a sound hole or opening in the body. It may be either fretted or unfretted.

More specifically, the term "lute" can refer to an instrument from the family of European lutes. The term also refers generally to any string instrument having the strings running in a plane parallel to the sound table (in the Hornbostel–Sachs system).

The strings are attached to pegs or posts at the end of the neck, which have some type of turning mechanism to enable the player to tighten the tension on the string or loosen the tension before playing (which respectively raise or lower the pitch of a string), so that each string is tuned to a specific pitch (or note). The lute is plucked or strummed with one hand while the other hand "frets" (presses down) the strings on the neck's fingerboard. By pressing the strings on different places of the fingerboard, the player can shorten or lengthen the part of the string that is vibrating, thus producing higher or lower pitches (notes).

The European lute and the modern Near-Eastern oud descend from a common ancestor via diverging evolutionary paths. The lute is used in a great variety of instrumental music from the Medieval to the late Baroque eras and was the most important instrument for secular music in the Renaissance. During the Baroque music era, the lute was used as one of the instruments which played the basso continuo accompaniment parts. It is also an accompanying instrument in vocal works. The lute player either improvises ("realizes") a chordal accompaniment based on the figured bass part, or plays a written-out accompaniment (both music notation and tablature ("tab") are used for lute). As a small instrument, the lute produces a relatively quiet sound. The player of a lute is called a lutenist, lutanist or lutist, and a maker of lutes (or any similar string instrument, or violin family instruments) is referred to as a luthier.