The film -- set in Los Angeles during the summer of 1969, when the infamous Manson Family murders took place and resulted in eight deaths -- will feature Dunham portraying a character named Gypsy, Variety reported. Dunham signed onto the project along with Austin Butler, Lorenza Izzo and Maya Hawke, the daughter of Ethan Hawke and Uma Thurman -- the star of Tarantino's Kill Bill and Pulp Fiction.
Hawke will portray a character named Flower Child with Izzo as Francesca Capucci, an Italian movie star.
The film's ensemble cast also includes Margot Robbie as late actress and Manson Family victim Sharon Tate, Leonardo DiCaprio as fictional television actor Rick Dalton, Brad Pitt as Dalton stunt double Cliff Booth, Dakota Fanning as Manson Family associate Lynette 'Squeaky' Fromme, Damian Lewis as actor Steve McQueen, Emile Hirsch, Burt Reynolds, Al Pacino, Timothy Olyphant, James Marsden and Tim Roth.
Once Upon a Time in Hollywood is set for release on July 26, 2019. The film was originally set to be released on Aug. 9 to coincide with the 50th anniversary of the Manson Family killings, named after convicted cult leader Charles Manson.
This is Dunham's first major film role after creating and starring in HBO's Girls. She has also appeared in an episode of American Horror Story: Cult and drama Tiny Furniture.