511th may refer to:
511th Bombardment Squadron, inactive United States Air Force unit 511th Heavy Panzer Battalion, German World War II independent armoured battalion equipped with heavy tanks 511th Parachute Infantry Regiment (United States), unit of the United States Army first activated during World War II 511th Tactical Fighter Squadron, inactive United States Air Force unit
See also 511 (number) 511 (disambiguation) 511, the year 511 (DXI) of the Julian calendar 511 BC