In the 2003 Teenage Mutant Ninja Turtles series, Shredder’s human identity is Oroku Saki.
Oroku Saki is presented as the leader of the Foot Clan and as a powerful opponent of the turtles. His identity is central to the series’ early conflict, linking criminal ambition, martial-arts training, and the turtles’ continuing struggle to protect their city.
The 2003 series also develops the idea that this Shredder is connected to the alien Utroms. That storyline differs from the simpler human-villain presentation found in some earlier adaptations and from other versions that use different identities or origins.
Names can be confusing because Karai, Hun, and Baxter Stockman are also important Foot Clan or villain characters in the 2003 continuity. They are not Shredder’s human identity in this series.