It used to be placed in the Old World warbler assemblage, but is now recognized as part of the marsh and tree-warbler family (Acrocephalidae). Great reed warblers are medium-sized birds and are the largest of the European warblers. They breed throughout mainland Europe and the west Palearctic and migrate to sub-Saharan Africa in the winter. Great reed warblers favour reed beds as their habitat during breeding months, while living in reed beds, bush thickets, rice fields, and forest clearings during the winter. Great reed warblers exhibit relatively low sexual dimorphism, and both genders of the species are similar in appearance. This species mates both polygynously and monogamously.