Smithy is a nickname for:
People Charles Kingsford Smith (1897–1935), Australian pioneer aviator Ian Smith (1919–2007), Prime Minister of Rhodesia and World War II Royal Air Force pilot Mike Smith (broadcaster) (1955–2014), British television and radio presenter, racing driver, pilot and businessman W. G. G. Duncan Smith (1914–1996), World War II flying ace
Fictional characters Smithy (Mario), the main villain of the video game Super Mario RPG Dale Smith (The Bill), in the television series The Bill Neil "Smithy" Smith, in the television series Gavin & Stacey Smithy, hero of stories by Edgar Wallace