Ariane Daniela Forster, known by her stage name Ari Up, was a German vocalist best known as a member of the English post-punk band The Slits. In 1976, at the age of 14, Up formed the Slits with drummer Palmolive.

Soon after the Slits were touring as the opening act for the Clash. Ari Up's love of reggae led the Slits into a "jungly" dub style. She was the most flamboyant member of the group, becoming known for her wild hair and stage outfits.