Robert Alexander McCallister is a fictional character on the ABC television series Brothers & Sisters. He is portrayed by Rob Lowe. Married to Kitty Walker, he was a Republican United States Senator from the state of California, a former candidate for President of the United States, and a former candidate for Governor of California.

Brothers & Sisters is an American family drama television series that centers on the Walker family and their lives in Los Angeles and Pasadena, California. The series aired for five seasons on ABC from September 24, 2006, to May 8, 2011. For the entirety of its run, it was broadcast on Sunday nights following Desperate Housewives.