A knot is a unit of speed equal to one nautical mile per hour, which is equal to exactly 1.852 km/h and approximately 1.151 mph.

The abbreviation kn is preferred by members of the International Hydrographic Organization (IHO), which includes all major seafaring nations, however the abbreviations kt (singular) and kts (plural) are also widely used.

The knot is a non-SI unit that is accepted for use within the SI scale.

Worldwide, the knot is used in meteorology, and in maritime and air navigation to measure the speed of a particular variable.

For example, a vessel traveling at 1 knot along a meridian travels one minute of geographic latitude in one hour.

Mariners first used the term 'knot' denoting the measure of how many knots in a special line paid out in a given time, using the chip log.