region in central Africa bordering on Lake Albert Nyanza (now Lake Albert), on the west bank of the Upper Nile, that was administered by the Congo Free State in 1894–1909 and was incorporated thereafter into the Anglo-Egyptian Sudan.

Europeans first visited the northern part of the region in 1841–42, when an expedition was dispatched there by Muḥammad ʿAlī Pasha, the Ottoman sultan of Egypt. The neighbouring posts of Gondokoro, on the east bank, and Lado soon became stations for ivory and slave traders from Khartoum. After the discovery of Lake Albert Nyanza in 1864 by the British explorer Sir Samuel Baker, the whole region was overrun by slave raiders of diverse nationalities. Although Lado was claimed as part of the Egyptian Sudan, it was not until Baker arrived at Gondoroko in 1870 as governor of the equatorial provinces that any attempt to control the slave trade was made. Baker's successor, General C.G. Gordon (Gordon, Charles George), established a separate administration for the Baḥr al-Ghazāl (a southern province of the present-day republic of The Sudan). In 1877 Emin Paşa (Emin Pasha, Mehmed) (a German administrator) became governor of the equatorial provinces and made his headquarters at Lado, whence he was driven in 1885 by Mahdists from the Sudan. He then removed southward to Wadelai, but in 1889 he was forced to withdraw to the east coast. The British claimed the Upper Nile region in February 1894, and that May they leased to Leopold II of Belgium, as sovereign of the Congo State, a large area west of the Upper Nile, which included the Baḥr al-Ghazāl and Fashoda. Pressed by France, however, Leopold agreed to occupy only that part of the area east of 30° E and south of 05°30′ N; thus, the actual limits of what was later called the Lado Enclave (the region occupied by Leopold) were defined.

After the French withdrew from Fashoda (1898), Leopold II revived his claim to the whole area leased to him by the British. Although he was unsuccessful, and the lease was annulled as a result of a new agreement with Great Britain, Leopold retained the enclave, with the stipulation that it should revert to the Anglo-Egyptian Sudan six months after the end of his reign. After Leopold's death in 1909, the Lado Enclave was incorporated into the Anglo-Egyptian Sudan in 1910.