Rei Juckernaut (レイ・ジャガーノート Rei Jagānōto) is a Meister Otome in Mai-Otome 0~S.ifr~, and Garderobe's Third Column who wields the GEM the Intensely Playing Peridot.
She joins Principal Una Shamrock in her efforts to track down and kill Sifr Fran and, with Fourth Column Kyoko Tsumabuki, fights alongside Una in her futile battle against Lena Sayers (the Fifth Column, Iruma Van de Veld, is also involved, though, as she is armed with a gun, she is remote from the immediate battlefield). Alongside Kyoko and Iruma, Rei is suspended from her duties by Maria Graceburt for her part in Garderobe's interference in Windbloom's political affairs.