William Boyd is the name of many notable people: William Boyd (actor), better known as "Hopalong Cassidy" William Boyd (bassist) William Boyd (Colonel), United States Army Air Forces, base commander, Selfridge Field, Michigan, reprimanded in 1944 for ordering racially-segregated facilities for officers in violation of War Department regulations. (See Freeman Field Mutiny.) William Boyd (pathologist) William Boyd (writer) William Boyd (Moderator), former Moderator of the Presbyterian Church in Ireland William C. Boyd, the US immunologist William Lemuel Boyd, western musician William Boyd, 3rd Earl of Kilmarnock (died 1717) William Boyd, 4th Earl of Kilmarnock (1704-1746)