The speed of light, also referred to as light-speed, or the warp threshold, is the velocity that photons travel in a vacuum. Commonly denoted by the variable c, the speed of light is roughly equivalent to 300,000 kilometers per second.
Light-speed is equivalent to Warp 1. The Phoenix, piloted by Zefram Cochrane, was Earth's first ship to travel faster than the speed of light. (Star Trek: First Contact)