Marsh Warbler, Acrocephalus palustris, is a species of passerine bird in the warbler family found in wetland and river and lake ecosystems. It is widely distributed across the Eastern, Central and north-Western Europe. This species favours rank, tufty and fairly tall herbage, especially nettles (Urtica), meadowsweet (Filipendula ), brambles (Rubus fruticosus) and others, often in the vicinity of taller bushes or trees. It also occurs in corn fields and other agricultural land surrounded with a belt of low bushes or hedgerows as well as in wasteland with tall grass, herbs and small bushes, in tall herbaceous vegetation along ditches, in marsh vegetation at edges of swamps, in reeds on dry ground and even in gardens (European Red List 2015).

Acrocephalus palustris has a breeding population size of 2200000-3430000 pairs and a breeding range size of 1830000 square kilometres in the EU27. The breeding population trend in the EU27 is Stable in the short term and Stable in the long term.

The EU population status of Acrocephalus palustris 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).