The Acrocephalidae (the reed warblers, marsh- and tree-warblers, or acrocephalid warblers) are a family of oscine passerine birds, in the superfamily Sylvioidea. The species in this family are usually rather large "warblers". Most are rather plain olivaceous brown above with much yellow to beige below. They are usually found in open woodland, reedbeds, or tall grass. The family occurs mostly in southern to western Eurasia and surroundings, but also ranges far into Pacific, with some species in Africa.