Slieve Gullion (from Irish: Sliabh gCuillinn, meaning "mountain of the steep slope" or Sliabh Cuilinn, "Culann's mountain") is a mountain in the south of County Armagh, Northern Ireland.
 
The mountain is the heart of the Ring of Gullion and is the highest point in the county, with an elevation of 573 metres (1,880 ft). At the summit is a small lake and two ancient burial cairns, one of which is the highest surviving passage grave in Ireland.
 
Slieve Gullion plays a prominent role in the mythology and history of the area and dominates the countryside around it, offering views of as far away as Antrim, Dublin Bay and Wicklow on a clear day.