Sonbai (also spelt Sonnebay, Sonba'i, or Sonbait) was an Indonesian princely dynasty that reigned over various parts of West Timor from at least the 17th century until the 1950s.
The ancestor of the line, who was a brother of the Liurai (ruler) of Wehali, migrated to the highlands of West Timor, where he married a daughter of a local Atoni lord, Kune, and inherited his lands.
In 1655 Sonbai switched sides and made a contract with the Dutch East Indies Company (VOC), the enemies of the Portuguese colonialists.
The new Kupang principality was governed by members of the Nisnoni family, a side-branch of Sonbai, surviving the Japanese occupation of the Dutch East Indies in 1942-45 and the Indonesian Revolution in 1945–49.
The rulers, known to the Europeans as "emperor (keizer, imperador)",[4] usually had an inactive role, while the executive governance was done by their main lieutenants of the Kono family.