The Tezaarians were a pre-warp species native to the planet Tezaar.

Hundreds of years before the 23rd century, the Tezaarians were in danger of planetary collapse. The Vulcans saved their civilization by providing them with the technology to sustain themselves, including a nuclear power system that supplied energy to their entire world.

In 2261, the Tezaar Nuclear Power Facility malfunctioned and threatened a planet-wide nuclear meltdown. No Vulcans were in range to assist, and the Prime Directive forbade Federation personnel of any other species from intervening. Furthermore, Tezaarian scanner technology was advanced enough to penetrate superficial disguises. The USS Enterprise therefore dispatched an away team, whose Human members were transformed into Vulcans via the Kerkhovian serum, to effect the necessary repairs. (SNW: "Four-and-a-Half Vulcans")