William Emmerson (born October 28, 1945) is a former Republican California State Senator who represented the 23rd district in Riverside County. He previously represented the 37th Senate District, having been elected in a June 8, 2010, special election and sworn into office the next day. Preceding his tenure in the State Senate, Emmerson served as California State Assemblyman from the District 63 representing the counties of Riverside and San Bernardino, having been first elected in November 2004.