Miles per hour (mph, m.p.h., MPH, or mi/h) is a British imperial and United States customary unit of speed expressing the number of miles travelled in one hour.

Speed limits and road traffic speeds are given in miles per hour in the following jurisdictions: Miles per hour is the unit used on the US, Canadian and Irish rail systems.

[32][33][34] Miles per hour is also used on British rail systems, excluding trams, some light metro systems, the Channel Tunnel and High Speed 1.

[35] Nautical and aeronautical applications favour the knot as a common unit of speed.

In some countries mph may be used to express the speed of delivery of a ball in sporting events such as cricket, tennis and baseball.