William Robert "Bob" Holcomb (March 1, 1922 – November 29, 2010) was an American politician and attorney. Holcomb was the longest serving mayor of San Bernardino, California, to date. He held office as San Bernardino's mayor from 1971 until 1985, and returned to office again from 1989 until 1993. Holcomb has been widely credited with preserving the independence of the San Bernardino Valley Municipal Water District and its local water supply.