231st may refer to: * 231st Battalion (Seaforth Highlanders of Canada), CEF, a unit in the Canadian Expeditionary Force during the First World War * 231st Combat Communications Squadron, a tenant unit of the 113th Wing based at Andrews Air Force Base, Maryland, USA * 231st Infantry Brigade, the Allied codename for the centre invasion beach during the World War II Allied invasion of Normandy, 6 June 1944