Kosaku Sumiyoshi (Japanese: 住吉 耕作; 1 October 1907 – 1971) was a Japanese track and field athlete. He represented his country twice at the Summer Olympics (1928 and 1932) and was the first Asian to compete in the Olympic javelin throw. He was a three-time gold medallist at the Far Eastern Championship Games and the only person to win two javelin titles at the competition.