Robert Swan Mueller III (; born August 7, 1944) is an American lawyer who served as the sixth director of the Federal Bureau of Investigation (FBI) from 2001 to 2013.

A graduate of Princeton University and New York University, Mueller served as a Marine Corps officer during the Vietnam War, receiving a Bronze Star for heroism and a Purple Heart. He subsequently attended the University of Virginia School of Law. Mueller is a registered Republican in Washington, D.C., and was appointed and reappointed to Senate-confirmed positions by presidents George H. W. Bush, Bill Clinton, George W. Bush, and Barack Obama.

Mueller has served both in government and private practice. He was an assistant United States attorney, a United States attorney, United States assistant attorney general for the Criminal Division, a homicide prosecutor in Washington, D.C., acting United States deputy attorney general, partner at D.C. law firm WilmerHale and director of the FBI. He is the only FBI Director that Congress has allowed to serve more than the statutory limit of 10 years since the death of J. Edgar Hoover in 1972 by giving him a special two-year extension.

On May 17, 2017, Mueller was appointed by Deputy Attorney General Rod Rosenstein as special counsel overseeing an investigation into allegations of Russian interference in the 2016 U.S. presidential election and related matters. He submitted his report to Attorney General William Barr on March 22, 2019. On April 18, the Department of Justice released it. On May 29, he resigned his post and the Office of the Special Counsel was closed.