The fourth season of Stargate Atlantis, an American-Canadian television series, began airing on September 28, 2007 on the US-American Sci Fi Channel. The fourth season concluded after 20 episodes on March 7, 2008 on Sci Fi. The series was developed by Brad Wright and Robert C. Cooper, who also served as executive producers. Amanda Tapping (Col. Samantha Carter) joins the cast as a regular for 14 episodes, Jewel Staite (Dr. Jennifer Keller) was a recurring character for eleven episodes, while regular cast member Torri Higginson (Dr. Elizabeth Weir) was a recurring cast member for four episodes. Other season four regular cast members include Joe Flanigan, David Hewlett, Rachel Luttrell and Jason Momoa.