Parathalassius is a genus of flies in the family Dolichopodidae.

It is found along sandy sea coasts in both the Palaearctic and Nearctic realms.

[1] The name "Parathalassius" is of Greek origin, and can be translated as "near the sea".

[2] Parathalassius capensis Smith, 1972[4] was moved to Plesiothalassius.

This article related to members of the fly family Dolichopodidae is a stub.