Mamoru Yamaguchi (born May 29, 1977) is a Japanese mixed martial artist who competes in Pancrase.

These victories entitled win a fight for the inaugural Shooto Featherweight (132 lb) Championship, in a rematch against Jin Akimoto.

He was given a chance to win the inaugural Shooto Bantamweight (123 lb) Championship, when he faced Yasuhiro Urushitani.

He went on a four fight winning streak, most notably beating Junji Ikoma, before defending the bantamweight title for the second time against Shinichi Kojima.

Moving to King of the Cage he won the junior flyweight title by defeating Frank Baca with a rear naked choke.

[14] He fought Greg Guzman next, but the fight wasn't a title defense, as his opponent missed weight.