Polybius navigator is a species of crab in the family Polybiidae.
Polybius navigator is found chiefly around the British Isles; its range covers the northeast Atlantic Ocean, including the North Sea as far north as Trøndelag in Norway, and as far south as Mauritania, and it also occurs in the Mediterranean Sea.
Polybius navigator has a dark brown carapace up to approximately wide, with lighter pereiopods. The frontal margin of the carapace, between the eyes, has a fringe of hair but no spines.
Two subspecies are recognised: