The Macquarie Marshes are located in the lower reaches of the Macquarie River in central west New South Wales, and stretch north of the township of Warren. The extent of the greater Macquarie Marshes (approximately 200,000 hectares) is defined by flood patterns and vegetation types. The Marshes include areas inundated by flows from the Macquarie River and its distributary streams and anabranches, including Marebone Break, Bulgeraga Creek, Buckiinguy Creek, Monkeygar Creek, Old Macquarie River, Bora Channel, the Ginghet, Mullins Swamp, Gum Cowal–Terrigal Creek to its confluence with Marthaguy Creek, Long Plain Cowal and Dusty Swamp.
The Macquarie Marshes Ramsar site was designated in 1986 and covers about 10% of the area of the Marshes. The Ramsar site contains core areas of semi-permanent wetland vegetation, sites of great importance for waterbird breeding, and habitat for a large number of wetland-dependent faunal species. Sections of the site are on private properties used for sustainable cattle grazing on native pastures.