Gretchen Mol (born November 8, 1972) is an American actress and former model. She is known for her role as Gillian Darmody in the HBO series Boardwalk Empire (2010–2014). She also appeared in the films Rounders (1998), Celebrity (1998), The Thirteenth Floor (1999), The Notorious Bettie Page (2005), in which she played the title character, 3:10 to Yuma (2007), and Manchester by the Sea (2016).