Ernest Gary Gygax ( July 27 , 1938 -- March 4 , 2008 ) ( IPA : ( Ë gaj . gÃ ks ) ) was an American writer and game designer , best known for co-creating the early role-playing game Dungeons & Dragons ( D&D ) with Dave Arneson in 1974 . Ernest Gary Gygax ( July 27 , 1938 â `` March 4 , 2008 ; last name pronounced ) was an American writer and game designer best known for co-creating the pioneering role-playing game Dungeons & Dragons ( D&D ) with Dave Arneson .