The Alpha Centaurans, also known as Centaurians or Centaurans, were a humanoid species from Alpha Centauri VII. Physically, they are indistinguishable from humans. Scientists had found evidence to suggest that they were descended from Humans transplanted from Ancient Greece. (The Worlds of the Federation)

First contact between Centaurians and Humans was made by the SS Pioneer in 2066. (Ship Recognition Manual, Volume 4: Starships of the Original Series Era)

According to the fan fiction series Star Trek: Pendragon the Centaurians and Centaurans were two distinct Centaurii species.