This article contains two lists of countries by length of coastline, in kilometers. A coastline of zero indicates that the country is landlocked.
The coastline paradox states that a coastline does not have a well-defined length. Measurements of the length of a coastline behave like a fractal, being different at different scale intervals (distance between points on the coastline at which measurements are taken). The smaller the scale interval (meaning the more detailed the measurement), the longer the coastline will be. This "magnifying" effect is greater for convoluted coastlines than for relatively smooth ones. Treated as fractals, coastlines can however be measured. For example, the coast of Great Britain has a size of about 28000 km1.43, which is called its Hausdorff measure.