Sultanate & Colonial Era

The Sultanate of Brunei controlled much of western and northern Borneo for several centuries, while the Sultanate of Sulu held the northeastern regions. Both sultanates granted territories to European powers through a series of agreements in the 18th and 19th centuries — agreements whose legal interpretation remains disputed and forms part of the current sovereignty question.

Spanish, Dutch, and British powers all sought influence in Borneo during the colonial era. The Dutch established dominance in the south (now Indonesian Kalimantan), while the British consolidated their presence through a series of treaties. James Brooke became the Rajah of Sarawak in 1841, while separate arrangements were made for the territory that would become British North Borneo.

A foundational dispute in Sabah's sovereignty question concerns the 1878 agreement between the Sultan of Sulu and the Overbeck-Dent syndicate. The Malay version of that agreement uses the word "pajakon" (lease), while the English version speaks of "cession" (permanent transfer). This crucial discrepancy — never properly resolved — forms part of the legal basis for asserting that North Borneo's sovereignty was never definitively transferred.