A mandolin (Italian: mandolino pronounced [mandoˈliːno]; literally “small mandola”) is a stringed musical instrument in the lute family and is usually plucked with a plectrum. It commonly has four courses of doubled metal strings tuned in unison (8 strings), although five (10 strings) and six (12 strings) course versions also exist. The courses are typically tuned in a succession of perfect fifths, with the same tuning as a violin. It is the soprano member of a family that includes the mandola, octave mandolin, mandocello and mandobass.

There are many styles of mandolin, but three are common, the Neapolitan or round-backed mandolin, the carved-top mandolin and the flat-backed mandolin. Each style of instrument has its own sound quality and is associated with particular forms of music. Neapolitan mandolins feature prominently in European classical music and traditional music. Carved-top instruments are common in American folk music and bluegrass music. Flat-backed instruments are commonly used in Irish, British and Brazilian folk music. Some modern Brazilian instruments feature an extra fifth course tuned a fifth lower than the standard fourth course.

Mandolins evolved from the lute family in Italy during the 17th and 18th centuries, and the deep bowled mandolin, produced particularly in Naples, became common in the 19th century. Following its invention and early development in Italy the mandolin spread throughout the European continent. The instrument was primarily used in a classical tradition with Mandolin orchestras, so called Estudiantinas or in Germany Zupforchestern appearing in many cities. Following this continental popularity of the mandolin family local traditions appeared outside Europe in the Americas and in Japan. Travelling mandolin virtuosi like Giuseppe Pettine, Raffaele Calace and Silvio Ranieri contributed to the mandolin becoming a “fad” instrument in the early 20th century. This “mandolin craze” was fading by the 1930s, but just as this practice was falling into disuse, the mandolin found a new niche in American country, old-time music, bluegrass and folk music. More recently, the Baroque and Classical mandolin repertory and styles have benefited from the raised awareness of and interest in Early music.