David Reubeni (1490–1535/1541?)

is a Jewish political activist, described by the Shengold Jewish Encyclopedia as "half-mystic, half-adventurer."

Although some scholars are reluctant to believe his claims to nobility, citing suspicions of fraud behind such claims[ (in spite of Reubeni's unrelenting efforts to make an alliance between Christians and Jews against Muslims by the intermediation of the young king, John of Portugal), in November of 1525 he is nevertheless given an audience with the king, accompanied with a letter of recommendation from Pope Clement VII, and has always insisted that he was the son of a deceased monarch (King Suleiman of Ḥabor), and that he was the Minister of that kingdom's War Department, now governed by his elder brother, King Joseph of Ḥabor.

According to Reubeni's own story this kingdom has three hundred thousand "Israelite" subjects.

The king of Portugal, impressed by the idea, initially agrees to supply Reubeni with Portuguese arms, but after five months, Reubeni falls into ill-repute with the king of Portugal, who perhaps distrusts his motives, and is asked by the king to leave his kingdom.