Question: who played the original steve mcgarrett on hawaii five-o?
Answer: Jack Lord, John Joseph Patrick Ryan

John Joseph Patrick Ryan ( December 30 , 1920 -- January 21 , 1998 ) , best known by his stage name , Jack Lord , was an American television , film and Broadway actor and director and producer . He was known for his starring role as Steve McGarrett in the CBS television program Hawaii Five - O , which ran from 1968 to 1980 .