Isla Lang Fisher (; born 3 February 1976) is an Australian actress and author. Born to Scottish parents in Oman, she moved to Australia at age six. After appearing in television commercials and guest-starring in an episode of Paradise Beach, Fisher took on the regular role of Shannon Reed on the soap opera Home and Away (1994–97), garnering two Logie Awards nominations.

She made the transition to Hollywood in the live-action comedy Scooby-Doo (2002), and has since risen to international prominence for her roles in the films Wedding Crashers (2005), Horton Hears a Who! (2008), Confessions of a Shopaholic (2009), Rango (2011), The Great Gatsby (2013), and Now You See Me (2013). Her other notable film credits include I Heart Huckabees (2004), The Lookout (2007), Definitely, Maybe (2008), Bachelorette (2012), Rise of the Guardians (2012), Keeping Up with the Joneses (2016), and Nocturnal Animals (2016). She also plays a recurring role in the fourth and fifth seasons of Arrested Development (2013, 2018).

In addition to acting, Fisher has authored two teen novels and the Marge in Charge book series.