Isao Koizumi (小泉 勲, Koizumi Isao, born July 2, 1945) is a Japanese former volleyball player who competed in the 1968 Summer Olympics.

Olympic medal record
Men's Volleyball
Silver medal – second place 1968 Mexico City Team

In 1968 he was part of the Japanese team which won the silver medal in the Olympic tournament. He played all nine matches.

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