The fastest rotating stars are known as "rapid rotators". These stars can spin at speeds of several hundred kilometers per second at their equator, completing a full rotation in just a few hours or even minutes. One of the most extreme examples is the star Achernar, which rotates so quickly that it is almost spherical in shape. Achernar spins at a speed of approximately 250 kilometers per second at its equator, completing one full rotation in just over 6 hours.