Umbar was a realm on the coast south of Gondor in Middle-earth. It was also the name of the great cape and land-locked firth and of the natural haven in this realm. It was probably also the name of a fortified city in this realm, because the name Umbar was used in conjunction with it being made into a great fortress, it being laid siege to or it being invested, which implies a very small fortified area.

Umbar was located south of the mouth of the river Anduin at the Bay of Belfalas in a natural haven that was formed by a peninsula that extended west from the coast of the Belegaer sea and then bent to the south and almost touched the coast that lay to its south. This form of the coastline left only a narrow entrance to the natural haven. The City of the Corsairs was at the easternmost point of the bay of Umbar. Umbar was the nearest to Gondor of the realms of the Harad. It is possible that the realm of Umbar stretched along the coast up to the river Harnen and along the river Harnen as far its source in the Ephel Dúath before it became a part of Gondor or after it became an independent realm again, because Westron was still the native tongue in this area at the time of the War of the Ring. It is possible that Umbar had a climate that was fluctuating between mild winters and very hot and dry summers. It is also possible that Umbar had a vegetation of sparse woodlands, because Umbar seems to have had the natural resources to build a fleet of fifty great ships and smaller vessels beyond count that had attacked Pelargir during the War of the Rings thirty nine years after Argagorn had burnt a great part of the ships of the Corsairs in the haven of Umbar.