The third season of the American television medical drama Grey's Anatomy, commenced airing on the American Broadcasting Company (ABC) on September 21, 2006, and concluded on May 17, 2007. The season was produced by Touchstone Television, in association with Shondaland Production Company and The Mark Gordon Company, the showrunner being Shonda Rhimes. Actors Ellen Pompeo, Sandra Oh, Katherine Heigl, Justin Chambers, and T.R. Knight reprised their roles as surgical interns Meredith Grey, Cristina Yang, Izzie Stevens, Alex Karev, and George O'Malley, respectively, continuing their expansive storylines as focal points throughout the season. Previous main cast members Chandra Wilson, James Pickens, Jr., Kate Walsh, Isaiah Washington, and Patrick Dempsey also returned, while previous guest stars Sara Ramirez and Eric Dane were promoted to series regulars, following the extension of their contracts.