Sumbawa is a relatively large but sparsely populated island in eastern Indonesia, traditionally forming the eastern frontier of Islam in this part of the Southeast Asian Archipelago. In the early-modern era the Sumbawan sultanates Bima and Dompu increased their manpower through a system of slave acquisition which is little known in the extant literature on Southeast Asian bonded labour. Slaves were acquired from the non-Muslim islands to the east, such as Flores and Sumba. Moreover, internal warfare on Sumbawa led to enslavement. Many slaves were put to work in settlements directly subservient to the royal courts, while others served in the various villages. The paper further discusses how the bonded labour relations were transformed in the 19th and 20th centuries due to negotiation between the old elites and the encroaching colonial state, and how the bonded status in the villages also eroded due to economic changes in the late colonial era.