Kazuo Matsui (born 23 October 1975 in Osaka) is a Japanese baseball player. His nickname is Kaz. He was a second baseman and shortstop. He played for the Houston Astros. He also played for the Colorado Rockies and the New York Mets. In 2011, he began playing for the Tohoku Rakuten Golden Eagles.He played for the Seibu Lions from 1995 to 2003 and played for them again in 2018.