Summer Phoenix, born 10 December 1978 in Winter Park, Florida, is an American actress and model and a graduate of the New York University's Tisch School of the Arts.

Known mostly for being the younger sister of River Phoenix and Joaquin Phoenix, Summer has appeared in a few artistic / indie movies, including Wasted , The Laramie Project, Esther Kahn , SLC Punk!, and The Faculty. She also had guest television roles on ER, Growing Pains, Murder, She Wrote, and Airwolf.

Formerly a member of Causey Way , along with her sister Rain Phoenix (whose album she plays piano on), Summer also appeared, along with Matt Damon and Casey Affleck, at the Garrick Theatre in London, performing This is Our Youth in 2002. She has also performed with Clea Duvall.

Allegedly, Summer was named due to her family's happy reaction to returning to the United States after leaving the Children of God. She is an avid supporter of several environmental causes.

Summer Phoenix became engaged to Casey Affleck on December 25 2003, and gave birth to a son, Indiana August, on May 31 2004, in Amsterdam.