Daijiro Matsui (born December 5 ,1972 in Okayama, Japan) is a professional Japanese mixed martial arts fighter. Matsui made his mark in MMA mostly in PRIDE Fighting Championships, where he had a number of entertaining matches and respectable efforts, but few wins. Matsui's most well known victory came when he defeated Jose "Pele" Landi-Jons by majority decision in an incredible come from behind victory.

"Pele" knocked down Matsui, and it appeared that Matsui was unconscious, however Matsui was able to rally back and gain a decision victory. Matsui is known for his unorthodox striking when in a tight situations, a good example being the shoulder strike from the guard. Since 2004 he fought in smaller promotions, including Cage Rage and Pancrase, and has found somewhat better success in these smaller arenas.

He trained under Nobuhiko Takada. Matsui has recently left the Takada Dojo with longtime training partner Kazushi Sakuraba.