H&M, the world's number two clothes retailer after Zara owner Inditex,, has previously linked itself with Madonna and Stella McCartney.
Marni will be the latest house to collaborate with H&M on an exclusive collection, following Comme des Garcons, Jimmy Choo, Lanvin, Karl Lagerfeld and, most recently, Versace.
H&M said Marni was famed for its "original prints and inventive spirit".
H&M, whose high street rivals include Gap, Marks & Spencer and Next, said in July it was to partner with soccer star David Beckham to sell his new range of underwear. (Reporting by Helena Soderpalm; Editing by Dan Lalor)