Greta Kline (born March 21, 1994), better known by her stage name Frankie Cosmos, is an American musician and singer-songwriter from New York City, New York.

She is known for her independent releases, inspired by Frank O'Hara’s poetry, DIY ethics of K Records and the early-2000s New York City’s anti-folk scene. Kline is also the former bass guitarist of the band Porches. She is the daughter of actors Kevin Kline and Phoebe Cates.