"The Teacher" was a male Vulcan instructor of Spock's prior to his entry to Starfleet Academy. During his school days, the Teacher moderated a competitive test of logical reasoning between Spock and his fellow student, Salak. The Teacher attempted to assist Spock in this test by urging him to employ the methods of Chaotic Response Suppression. (TOS short story: "Chaotic Response")

This Teacher is never given a proper name. He is seen only in a hallucinatory memory of Spock's, and thus may have only been an invention of his imagination.