Una Shamrock
Character Information
Allegiance: Garderobe
Master: Fumi Himeno
Occupation: Column II, Principal
GEM: Bewitching Smile Amethyst
Age: 21 (0~S.ifr~)
Height: 166 cm (' ")
Weight: 51 kg ( lbs.)
B/W/H: 88/58/85

Una Shamrock (Japanese: ウーナ・シャムロック, Ūna Shamrock), voiced by Houko Kuwashima, is a character in Mai-Otome 0~S.ifr~.

She is the Principal of the Garderobe Academy, as well as a Meister Otome and the Second Pillar, bearing the GEM, the Bewitching Smile Amethyst, later borne by the Third Column Shizuru Viola.

Una's reaction in the wake of discovering that Sifr Fran is a scion of Windbloom's royal family is negative, resolving that the girl presents a danger to world stability and thus must be eliminating, ordering First Column Elliot Chandler to dispatch Sifr, calculating that she'll have easy access due to her friendship with Sifr's guardian Lena Sayers. When asked by Sifr why Una feels she must die, Una states that the royal family of Windbloom, by producing her, have reneged on an age old agreement between themselves and Garderobe. It must be noted that Windbloom's royal line - especially, it seems, the females - have certain abilities to operate technology which could cause great deals of damage to the world in its current, Garderobe-regulated state (cf Sifr's biological daughter Nina Wáng and her ability to use the Harmonium). Sifr herself has displayed these abilities as Schwartz' unwilling accomplice, awakening M-9 and vapourising a mountain using weapons on Schwartz' satellite.

To this purpose, and unaware of Elliot's defection, Una and the other three Columns set off into the desert seeking Sifr, much to the disapproval of Maria Graceburt. This enterprise resulted in Una and three of her Column colleagues (with the exception of Ellie, whose powers had been revoked by Una for her promise to defend Sifr) being comprehensively beaten by Lena, who had hacked into the Administar and summoned a robe, Artemis, using Highly Advanced Materialising Equipment.

Upon her return to Garderobe, Una was stripped of office by Maria, citing her interference in politics, and her colleagues suspended for a time.

Many fans of the Mai-HiME/Otome franchise believe that Una is the possible mother of Meister Otome Shizuru Viola.