Far Harad was a region in the far south of Middle-earth with undefined borders. It was a hot and sunny region and its peoples were generally dark skinned. From the time that Sauron first occupied Mordor, at around SA 1000, the peoples of Far Harad had been allied with him.

Men of Far Harad were in the forces that fought against Gondor in the Battle of the Pelennor Fields and they were described as powerful black-skinned men, looking like half-trolls. They fought hard but were ultimately defeated after Aragorn came ashore from the captured ships of the Corsairs.
Encyclopedia entry originally written by PotbellyHairyfoot