Slieve Donard sits at the northeastern edge of the Mournes, overlooking Newcastle and Dundrum Bay. It has two lesser summits on the seaward side - Millstone Mountain (460 m), and Crossone (540 m). Two glens separate Slieve Donard from the neighbouring mountains of Slieve Commedagh (to the northwest) and Chimney Rock Mountain or Slieve Neir (to the south). Slieve Commedagh, at , is the second-highest of the Mourne Mountains.