A surveying unit in U.S. Survey and International systems of Inch-Pound measure. Four chains measure 792 inches, 66 feet, 22 yards, or 4 rods, 1/10 of a furlong.
For purposes of land survey, it is divided decimally into hundredths called links (7.92"). There are 80 chains or 8000 links in a mile.
In the United States, the U.S. survey link and chain are approximately two parts per million larger than their international equivalents. Some U.S. states specify U.S. survey units, some specify international units, and some don't make a specification.