Shion Uzuki (シオン・ウヅキ) is the main protagonist and heroine of the Xenosaga series, with the exception of Xenosaga: Pied Piper, which focuses on Ziggy. She is the daughter of Suou Uzuki and Aoi Uzuki, and younger sister of Jin Uzuki.

In the beginning of the series, Shion is a Camelle Vector Industries First R&D Division computer scientist and programmer. She helped build KOS-MOS to combat the Gnosis because her deceased boyfriend Kevin Winnicot, original creator of KOS-MOS, was unexpectedly killed by the KOS-MOS Archetype.

In Xenosaga Episode I, Shion is Head and Chief Engineer of the KOS-MOS Project. Shion eventually quits Vector and joins the anti-U.M.N. underground resistance Scientia by Episode III. Shion seeks to save the universe from the Gnosis, as well as from an ancient religious cult known as Ormus.