Caitlin FitzGerald (born August 25, 1983) is an American actress and filmmaker. She is best known for her role as Libby Masters in the Showtime television drama Masters of Sex (2013–2016) and as the elusive Simone in Starz series Sweetbitter (2018–2019). She has appeared in Love Simple (2009), It's Complicated (2009), Gossip Girl (2011), Damsels in Distress (2011), Blue Bloods (2010), and Newlyweds (2011).

In 2010, she starred in a production of Hedda Gabler. In 2010, she also played the role of Benita in "After Hours", the 10th episode of the 1st season of the CBS crime drama, Blue Bloods. In 2012, she starred in and co-wrote the screenplay for the independent film Like the Water. In 2013, she starred as Liv in the independent romantic comedy ensemble Mutual Friends.