"Flat wound" refers to the manufacturing process of a string for an instrument, whereby the thickness or gauge characteristic is achieved by coiling a ribbon-like wire around the axial wire, as opposed to a round wire, as in the round wound string.

The resulting string is smooth and easy on the fingers, without the "ridges" of a round wound string, but has somewhat inferior flexibility and sustain. However, arguably certain types of music sound more authentic when played with flat wound strings.