Lower Yafa (Arabic: يافع السفلى Yāfi‘ as-Suflá), or the Sultanate of Lower Yafa (Arabic: سلطنة يافع السفلى Salṭanat Yāfi‘ as-Suflá), was a sultanate in the British Aden Protectorate ruled by the Al Afifi dynasty. Its capital was at Jaar. Lower Yafa was one part of Yafa'a, the other part being Upper Yafa. It is now part of the Republic of Yemen.

Soon after the British capture of Aden an engagement was entered into in 1839 with Ali bin Ghalib, Sultan of the Lower Yafai, similar to that concluded with the Abdali and Fadhli Sultans. It would be loyally adhered to.

Sultan Ali bin Ghalib died in 1841 at a great age, and was succeeded by his son, Ahmed bin Ali. He died in September 1873, and was succeeded by his son, Ali bin Ahmed, who was succeeded by his brother, Muhsin bin Ahmed, in May 1885. The latter died in July 1891, and his nephew, Sultan Ahmed bin Ali, was elected as his successor. The Government of India sanctioned the continuance to him, with effect from 20 July 1891, of the annual stipend of 250 dollars enjoyed by the late Sultan.

In 1873 hostilities broke out between the Yafai and the Fadhli, in consequence of the Yafai Sultan having repudiated an engagement, concluded on his behalf by his son and in the presence of the Resident at Aden, whereby he had consented to accept from the Fadhli Sultan a royalty of 25 dollars a year for the use of water for irrigation. For this breach of faith the stipend of the Yafai Sultan was temporarily withheld.

From 1888 to 1893 desultory strife, interrupted by short truces, was carried on with the Fadhli over the water-supply from the Naza channel. In 1893 a truce was made and was kept for several years.

In 1893 Sultan Ahmed bin Ali visited Aden on his way to Mecca, where he died on 27 June. He was succeeded by Sultan Bubakar bin Seif.

On 1 August 1895 a Protectorate Treaty was concluded between the British and the Lower Yafai.

In 1899 Sultan Bubakar bin Seif died. He was succeeded by Sultan Abdulla bin Muhsin.