A bowed string musical instrument, most often a violin. It is a colloquial term for the violin, used by players in all genres including classical music but perhaps most commonly folk music. The name is also that of a medieval instrument that is related to and somewhat resembles the modern violin.

Although violins and fiddles are essentially synonymous, the style of music played may determine specific construction differences between fiddles and classical violins. For example, fiddles may optionally be set up with a bridge with a flatter arch to reduce the range of bow-arm motion needed for techniques such as the double shuffle, a form of bariolage involving rapid alternation between pairs of adjacent strings. To produce a brighter tone, compared to the deeper tones of gut or synthetic core strings, fiddlers often use steel strings. The fiddle is part of many traditional (folk) styles, which are typically aural traditions - taught by ear rather than via written music.