Marielle Stiles Heller is an American director, screenwriter and actress. She is best known for directing the films The Diary of a Teenage Girl (2015), Can You Ever Forgive Me? (2018), and A Beautiful Day in the Neighborhood (2019), as well as acting in The Queen’s Gambit (2020).

The Diary of a Teenage Girl is a 2015 American comedy-drama film written and directed by Marielle Heller, based on the hybrid novel of the same name by Phoebe Gloeckner. It stars Bel Powley as a 15-year-old girl who becomes sexually active by starting a relationship with her mother's boyfriend. It also stars Kristen Wiig, Alexander Skarsgård, Christopher Meloni, Quinn Nagle, and Austin Lyon. It premiered at the 2015 Sundance Film Festival and had a limited release on August 7, 2015, by Sony Pictures Classics.