The Negril Great Morass is located in Negril, spanning both the parishes of Westmoreland and Hanover. The Morass is bordered by the Fish River Hills to the east and the Negril Hills to the south. In the west, the Morass is restricted by the narrow Long Bay strip and the Caribbean Sea.

The area comprises some 2,300 ha of wetlands comprising marshlands, mangrove forests, swamp forests and waterways. It is the island's second-largest wetland comprising one-fifth of such areas, and one of the largest coastal wetland ecosystems in the Caribbean. The southern end of the Morass features the Royal Palm Reserve. The area is a critical habitat for terrestrial and wetland bird species, including the vulnerable West Indian Whistling Duck (Dendrocygna arborea).

The Negril Great Morass falls within a declared Game Reserve, the Negril Environmental Protection Area (EPA) and the Negril Important Bird Area (IBA). Notwithstanding the importance and designated protections, the ecology and hydrology of this important wetland area face pressures from agriculture, planned and unplanned developments, and tourism. The lack of a buffer zone around the morass has detracted from the protection of the area given the immediate surrounding pressures such as tourism on the western reaches and quarrying and farming on the eastern sections. For example, Fish River Hill, on the eastern border is part of the Negril Quarry Zone.