Keith Victor Fahnhorst (February 6, 1952 – June 12, 2018) was a National Football League offensive lineman from 1974 through 1987. Fahnhorst, a 273-pound, 6-foot-6-inch lineman from the University of Minnesota, led the San Francisco 49ers in seniority and appeared in Super Bowl XVI and Super Bowl XIX games. Fahnhorst's younger brother Jim Fahnhorst played linebacker in the USFL and for the 49ers from 1984 to 1990. The brothers were teammates on the 1984 49ers team that won Super Bowl XIX and finished with a 15-1 record.