Agusan Marsh is a vast complex of freshwater marshes and water courses located in the province of Agusan del Sur in the Philippines. It supports the largest expanses of seven habitat types found in the country, including swamp forest and peat swamp forest. The marsh provides an important habitat for various water birds and threatened forest bird species. It is also home to the Indigenous Agusan Manobo people, who comprise 60% of the population and live within the western side of the marsh.