Mayuko Iwasa (岩佐 真悠子, Iwasa Mayuko, born February 24, 1987, in Nerima, Tokyo) is a Japanese entertainer/model. She was Miss Magazine 2003. Iwasa was awarded the Graph Prize, the 42nd Golden Arrow Awards (2004) in March 2005.

In June 2005, Iwasa recorded a duet with Naoya Ogawa called "Katte ni Shinryakusha" (An Invader in My Own Way), which was used as an ending song of Sgt. Frog. The two appeared on Music Station and Pop Jam. Iwasa was in the drama Gal Circle as Rika, a ganguro girl who scams her friends for money.