Ariane Daniele Forster, known by her stage name Ari Up, was a German vocalist best known as a member of the English punk rock band the Slits.

The Slits were a punk rock band based in London, formed there in 1976 by members of the groups the Flowers of Romance and the Castrators. The group's early line-up consisted of Ari Up and Palmolive, with Viv Albertine and Tessa Pollitt replacing founding members Kate Korus and Suzy Gutsy. Their 1979 debut album, Cut, has been called one of the defining releases of the post-punk era.