Abby Ryder Fortson (born March 14, 2008) is an American actress. She played Ella Novak in Transparent, Harper Weil in The Whispers, Sophie Pierson in Togetherness, Cassie Lang in Ant-Man (2015) and Ant-Man and the Wasp (2018), and Margaret Simon in Are You There God? It's Me, Margaret. (2023).

She is the daughter of actress Christie Lynn Smith and her husband, John Fortson.

On January 6, 2024, Fortson was honored with the Star on the Rise Award at the 2024 Astra Awards of the Hollywood Creative Alliance.