The kilometre per hour or kilometer per hour (symbol: km/h, km h-1 or km·h−1) is a unit of speed or velocity.

By definition, an object travelling at a speed of 1 km/h in a straight line for one hour moves one kilometre. The unit is the most commonly used unit of speed worldwide, more common than the SI unit of speed, metre per second (m/s or m s-1).