A fix, in navigation, is a determination of position using lines of position (LOPs), either from ranges and/or bearings to terrestrial objects, stars and planets, or from radio beacons on land or on satellites.

A fix is the result of the crossing of two or more lines of position, resulting in a single point, the fix. Using more lines will verify the results, and US Navy and Coast Guard consider two lines to constitute an esitmated position rather than an actual fix.