Kazuo Matsui (松井 稼頭央 Matsui Kazuo, born October 23, 1975 in Osaka, Japan) was a switch-hitting shortstop for the Seibu Lions in Japan from 1995 to 2003. His best year was 2002, when he hit .332 with 36 home runs, to go with 36 stolen bases.

Matsui now plays for the New York Mets in the US major leagues, having signed a 3-year contract prior to the 2004 season. He hit home runs in hs first at-bat of both the 2004 and 2005 baseball seasons: in 2004 he homered on the first pitch from Russ Ortiz of the Atlanta Braves leading off the first inning, and in 2005 on the sixth pitch from Paul Wilson of the Cincinnati Reds with one out in the first inning.