The State of Guanabara (Portuguese: Estado da Guanabara, ) was a former Brazilian state that existed from 1960 to 1975. It comprised the city of Rio de Janeiro, after the national capital was moved to Brasília in 1960. It was named after Guanabara Bay, which bordered its Eastern coast.
In 1834, the city of Rio de Janeiro became a municipality and was elevated to Imperial capital, but it was not part of any province (as Brazilian states were then called), having special status as the so-called "Neutral Municipality" (Portuguese: Município Neutro). When Brazil became a republic in 1889, the city of Rio de Janeiro remained the national capital and became the Federal District (Distrito Federal), while the surrounding province of Rio de Janeiro became a state, with Niterói as the state capital. So, for a long time there was an odd and confusing situation whereby the city of Rio de Janeiro was not located in the homonymous neighboring state. (An analogous situation exists today in Argentina with the Federal Capital of Buenos Aires and the separate Province of Buenos Aires, as well as in Mexico, with the Federal District containing the capital Mexico City that is not located in the neighbouring State of Mexico.)
With the moving of the national capital to Brasília in 1960, a new Federal District was carved out of the state of Goiás to contain it, while the old Federal District became the State of Guanabara.
Throughout its 15-year existence, Guanabara was a peculiar, even anomalous state in many ways. Comprising only one city (albeit a large one), Guanabara was the smallest Brazilian state. It also had the peculiarity of being the only state that had no 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 institutions there: the city of Rio de Janeiro was directly administered by the state government. On the other hand, this 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 these anomalies disappeared in 1975, when the states of Guanabara and Rio de Janeiro merged, retaining the name of Rio de Janeiro. The city of Rio de Janeiro became a new municipality and the capital of the new combined state.