Machadinho d'Oeste is a municipality located in the Brazilian state of Rondônia. Its population was 40,867 (2020) and its area is 8,509 km². The municipality contains part of the 346,861 hectares (857,110 acres) Jaru Biological Reserve, a fully protected conservation unit created in 1984.It also contains 13% of the Campos Amazônicos National Park, a 961,318 hectares (2,375,470 acres) protected area created in 2006 that protects an unusual enclave of cerrado vegetation in the Amazon rainforest.