Rondônia (, ; ) is one of the 26 states of Brazil, located in the North Region (the central-western part). It is bordered by Acre in the west,
Amazonas in the north, Mato Grosso in the east, and Bolivia in the south. Rondônia has a population of 1,815,000 as of 2021. It is the fifth least populated state. Its capital and largest city is Porto Velho, bathed by the Madeira River. The state was named after Cândido Rondon, who explored the north of the country during the 1910s. The state, which is home to c. 0.7% of the Brazilian population, is responsible for c. 0.3% of the Brazilian GDP.
The state has 52 municipalities and occupies an area of 237,590.547 km<sup>2</sup>, equivalent to the territory of Romania and almost five times larger than Croatia. In addition to this, there are other important cities such as Ariquemes, Cacoal, Guajará-Mirim, Ji-Paraná, Rolim de Moura and Vilhena.
Geography
left|thumb|Köppen map for Rondônia
thumb|right|upright=1.1|alt=Map of Rondônia showing tree-cover loss years, with forest remaining since 2000 in green and loss years shaded yellow through purple.|Tree-cover loss year in Rondônia, 2001-2024, from the [[Global Forest Change dataset.]]
Rondonia used to be home to over 200,000 km<sup>2</sup> of rainforest, but has become one of the most deforested places in the Amazon. By 2003 around 70,000 km<sup>2</sup> of rainforest had been cleared.
The area around the Guaporé River is part of the Beni savanna ecoregion.
The Samuel Dam is located in the state, on the Jamari River.
History
Pre-colonial
Before the Portuguese discovery of Brazil, the region where the present state of Rondônia is situated was populated by indigenous peoples, who are known to have included the following:
Arawan speaking peoples
- Aruás (Arawá language)
Chapacuran speaking peoples
- Oro-uins (Oro Win language)
Macro-Je speaking peoples
- Jabutis (Djeoromitxí language)
Nambikwaran speaking peoples
- Nambikwara (Nambikwara language)
Panoan speaking peoples
- Kaxarari (Kasharari language)
- Karipuna (Karipuna language (Jau-Navo))
Tupian speaking peoples
It is generally accepted by linguists that the area of modern Rondônia is the origin of the Tupian languages.
- Cinta Larga (Cinta Larga language)
- Gavião (Gavião language of Jiparaná)
- Paiter (Surui language)
- Amondauas (Kagwahiva language)
- Macurap (Makurap language)
- Sakurabiat (Mekéns language)
- Caritianas (Karitiâna language)
- Araras-caros (Ramarama language)
Peoples speaking language isolates
- Kanoê (Kanoê language)
- Kwazá (Kwazá language)
Colonial period
The Spaniard Ñuflo de Chávez was the first European explorer to reach the valley of the Guaporé River between 1541 and 1542, although he only passed through. Bandeirantes arrived in the region around 1650, with the goal of exploiting the gold and other minerals of the territory. In the same period, Jesuit priests came to the region and founded the first village.
thumb|363x363px|Forte do Príncipe da Beira, 1930.
As a consequence of the discovery of gold on the right bank of the Guaporé River, the Portuguese Crown founded the Captaincy of Mato Grosso in 1748 with as governor. On March 19, 1752, the governor designated Vila Bela da Santíssima Trindade as the capital, from where he commanded the border demarcation following the Treaty of Madrid (1750). In 1753, he installed a surveillance post in the village of Santa Rosa Velha, built by the Spanish on the right bank of the Guaporé, and thus in Brazilian lands. In 1759, the Spanish governor of Santa Cruz de la Sierra requested that the post be evacuated. Instead, Rolim de Moura built a fort to replace it, which became known as the . Due to the climate and the incursions of the Spanish, the Presidio was soon in ruins. It was rebuilt in 1769 by Governor Luís Pinto de Sousa Coutinho, and renamed as Forte de Bragança. Ruined again, in 1776 the Forte Príncipe da Beira was built in its place. In 1772, led an expedition from Belém which reached the Madeira River, the Mamoré River and the Guaporé River, reaching Santa Cruz de la Sierra. The decline of mining and the proclamation of the First Brazilian Republic caused the region to lose its economic importance until the end of the nineteenth century, when the exploitation of rubber entered its peak.
Postcolonial history
Rondônia's initial development was not driven by an official action by the Brazilian government. Rondônia was populated and integrated into the country thanks to the private initiative that was interested in the neighboring state of Acre, that was, at the time, at its economic peak, caused by the Amazon rubber boom. The clearing of the two contiguous areas in the 19th century is the result of the same expansion movement, the last in Brazil's territorial development cycle.
The definitive establishment of the former territory of Acre, in 1903, gave impetus to the development of the region of what is today Rondônia, as the Treaty of Petrópolis obliged Brazil to build the Madeira-Mamoré railway.
Decree-Law No. 5812 (13 of September 1943) established the was created from parts of the states of Amazonas and Mato Grosso. By the law of February 17, 1956, the region became known as the Federal Territory of Rondônia, in honor of Marshal Cândido Rondon. The exploitation of brazil nuts and rubber was the main economic activity until the discovery of cassiterite deposits, which accelerated the development and settlement of the region. In the 70s and 80s, tax incentives for private enterprises, federal government investments, as well as highway construction projects, the establishment of colonization centers and the easy access to good, cheap land stimulated migration, largely of peoples originating from the Center-South Region of Brazil. This development led to the territory achieving the status of a state in 1982, with 13 constituent municipalities, including the capital, Porto Velho. These are: Guajará-Mirim, Ji-Paraná, Vilhena, Ariquemes, Jaru, Pimenta Bueno, Colorado do Oeste, Cacoal, Ouro Preto do Oeste, Presidente Médici, Espigão d'Oeste and Costa Marques.