The Treaty of Demarcation and Exchange of Some Portuguese and Dutch Possessions in the Archipelago of Solor and Timor (Portuguese: Tratado de Demarcação e Troca de Algumas Possessões Portuguesas e Neerlandesas no Arquipélago de Solor e Timor) was a treaty signed between the Kingdom of Portugal (then ruled by Dom Pedro V) and the Netherlands (ruled by William III), on 20 April 1859, which demarcated the border between the colonies of the two kingdoms in the Indonesian Archipelago.
They were represented as plenipotentiaries on the Portuguese side by António Maria de Fontes Pereira de Melo, then Minister of Internal Affairs of the Kingdom of Portugal, and on the Dutch side by Maurits Jan Heldewier, chargé d'affaires of the Netherlands.[1]
By this treaty, Portugal ceded Larantuca, Sicca and Paga on the island of Flores, Wouré on the island of Adonara, and Pamung Kaju on the island of Solor. In return, the Netherlands ceded the kingdoms of Maubara and Ambeno, both on the island of Timor, as well the island of Ataúro. The treaty was ratified on 18 August 1860.