The Desert of Lostladen, also known as the Lothland desert and Lothlann, was a great desert in Near Harad that lay to the south of Mordor and to the east of the Harad Road in Haradwaith.
History
The Desert of Lostladen may have contained one of the great roads that led to Haradwaith and Rhûn where the soldiers of the Tower gained possession "of goods and booty and fresh slaves" from tributary lands which they then brought back to Mordor in "long waggon-trains" along one of the great roads.
Before the Battle of the Pelennor Fields, the Mordor-orcs crossed into the Desert of Lostladen beyond the Harnen river through the Narghil Pass, meeting with the Haradrim of Near Harad and the Corsairs of Umbar.
During the Last Debate, Aragorn II claimed that when they seized the Corsair fleet of Umbar on their way to the Pelennor Fields, the surviving Corsairs and the Haradrim among them had fled into the Desert of Lostladen.
Etymology
Lostladen is a Sindarin name meaning "empty and open", being comprised of the elements l(h)ost ("empty") and laðen/laden ("level, fair, equitable; smooth; open, cleared; flat; wide").