The Principality of Bethio (also spelled Bequio, Bekio, Bitio, Bétio or Beetyo) was a small monarchy located for centuries along the lower Senegal River valley, on the border between modern Mauritania and Senegal, in the northeast of Biffeche. In the 18th cetury it was also called the "Royaume d'Oral". Its capital was at Poum (now in the Kingdom of Biffeche), then moved to N'Dombo, and finally moved to Ross, Senegal in the 19th century (called Ross-Bethio since then). The original, fertile farmlands of Bethio are in a region just east of the Parc du Djoudj.

In the 18th century the most famous "Prince Bethio" was Maalixuri (Malichouri) who was legendary for his cleverness, changes of strategy, and defiance in disputes with the Kingdom of Waalo and with the French at Saint-Louis, Senegal.

Today, A. Diop, the current Prince Bethio, lives at Ross-Bethio where he is a Senegalese political leader.