The State of Guanabara (Portuguese: Estado da Guanabara, [ɡwanaˈbaɾa]) was a Brazilian city-state that existed from 1960 to 1975. It comprised only the city of Rio de Janeiro after the Federal District was moved from that city to Brasília in 1960. The state was named after Guanabara Bay, along its eastern coast.
In 1834, the city of Rio de Janeiro was elevated to Imperial capital of the Empire of Brazil, but it was not part of any Brazilian province, having special status as the so-called "Neutral municipality" (Portuguese: Município Neutro). The surrounding Province of Rio de Janeiro (which did not include the city) had its capital city in Niterói. When Brazil became a republic in 1889, the city of Rio de Janeiro remained the national capital and became the Federal District (Portuguese: Distrito Federal), while the surrounding homonymous province became a state, still with Niterói as its capital.
When the national capital was moved to Brasília in 1960, a new Federal District was carved out of the state of Goiás to contain it, and the old Federal District became Guanabara State.
Throughout its 15-year existence, Guanabara was a unique state in many ways. Comprising only one city (albeit a large one), Guanabara was the smallest Brazilian state by land. It also had the peculiarity of being the only Brazilian state that was not divided into municipalities. Although for some practical purposes, it was sometimes counted as having one single municipality, and Rio de Janeiro was officially named its capital, there was no mayor, municipal legislature or any other municipal government institution there, as the city of Rio de Janeiro was directly administered by the state government. On the other hand, that also meant that the Guanabara state government had some functions that were normally assigned to municipalities elsewhere, such as regulating urban zoning, inspecting the safety of buildings, or issuing licenses for commercial venues, for example.
All the characteristics disappeared in 1975, when the states of Guanabara and Rio de Janeiro merged into a new, larger State of Rio de Janeiro. The city of Rio de Janeiro became a municipality of the new combined state and its new capital city.