Ko Arima (有馬 洪, Arima Kō, born August 22, 1917) is a Japanese former football player.

He also played for University of Tokyo LB, which was composed of his alma mater University of Tokyo players and graduates.

At University of Tokyo LB, he won the 1949 Emperor's Cup with Masao Ono and the rest of the team.

In March 1951, when Arima was 33 years old, he was selected for the Japan national team for Japan's first game after World War II in the 1951 Asian Games.

This biographical article related to a Japanese association football midfielder born in the 1910s is a stub.