Western Marsh-harrier, Circus aeruginosus, is a species of day-flying bird of prey found in wetland and river and lake ecosystems.

Circus aeruginosus has a breeding population size of 37700-87900 breeding females and a breeding range size of 1670000 square kilometres in the EU27. The breeding population trend in the EU27 is Increasing in the short term and Increasing in the long term.

The EU population status of Circus aeruginosus was assessed as Secure, because the species does not meet any of the IUCN Red List criteria for threatened or Near Threatened, or the criteria for Depleted or Declining (the EU27 population or range has not declined by 20% or more since 1980).