Splinter is the name of the Teenage Mutant Ninja Turtles’ rat sensei.
He trains Leonardo, Raphael, Donatello, and Michelangelo in ninjutsu and serves as their adoptive father. Across the franchise, Splinter is usually depicted as an exceptionally skilled martial artist who emphasizes discipline, loyalty, restraint, and family.
His origin changes between versions. In the original comics and several adaptations, Splinter is a mutated rat who learned martial arts by observing or studying the human Hamato Yoshi. In other versions, Splinter is Hamato Yoshi himself, transformed into a rat after exposure to mutagen.
Those differing origin stories can cause confusion, but the name Splinter remains the turtles’ familiar title for their teacher and guardian. The character’s name also echoes the comic-book tradition of naming mentors after distinctive physical or conceptual traits.