A small instrument of the guitar family of Cuban origin. The most widespread variety of the instrument is the original Cuban tres with 6 strings in 3 double courses, which developed in the second half of the 19th century and was used to play changüí, a precursor of son. Its sound has since become a defining characteristic of the Cuban son and it is commonly played in a variety of Afro-Cuban genres. In the 1930s, the instrument was adapted into the Puerto Rican tres, which has 9 strings and a body similar to that of the cuatro.

The exact origins of the tres are not known, but it is assumed to have developed from the 19th century Spanish guitar, which it resembles in shape, as well as the laúd and bandola.

The Cuban tres is significantly smaller than the Spanish guitar, with a scale length between 19 and 26 inches. From the low pitch to the highest, the principal tuning is in one of two variants in C major, either: G4 G3, C4 C4, E4 E4 (top course in unisons) or, more traditionally: G4 G3, C4 C4, E3 E4 (top course in octaves).