Bob Denver ( January 9 , 1935 -- September 2 , 2005 ) was an American actor . He was best known for his roles as Gilligan on the 1960s television series Gilligan 's Island and Maynard G. Krebs on the earlier Many Loves of Dobie Gillis . Robert Osbourne `` Bob '' Denver ( January 9 , 1935 â `` September 2 , 2005 ) was an American comedic actor known for his roles as Gilligan on the television series Gilligan 's Island and the beatnik Maynard G. Krebs on the 1959 â `` 1963 TV series The Many Loves of Dobie Gillis .