The jig (sometimes seen in its French language or Italian language forms gigue or giga) is a folk dance type as well as the accompanying dance tune type, popular in Ireland and Scotland, and particularly associated with the former. It is a popular tune-type within the Irish dance music tradition, second only to the reel. It is transcribed in a time which is a multiple of three, 12/8 time for a 'single jig' or 'slide', 6/8 time for a 'double jig', and 9/8 time for a 'slip jig'.

The most common structure is two 8-bar parts, each of which is repeated (AABB). There are a number of tunes with three or more parts, and some in which the length of one or more parts varies from 8 bars. As with most other types of dance tunes in Irish music, at a session or a dance it is common for two or more jigs to be strung together, flowing on without interruption.