Is it true that Rio de Janeiro used to be the capital of the Kingdom of Portugal?

The transfer of the Portuguese court to Brazil occurred with the strategic retreat of Queen Maria I of Portugal, Prince Regent John, and the Braganza royal family and its court of nearly 15,000 people from Lisbon on November 29, 1807. The Braganza royal family departed for the Portuguese colony of Brazil just days before Napoleonic forces invaded Lisbon on December 1.

The Portuguese crown remained in Brazil from 1808 until the Liberal Revolution of 1820 led to the return of John VI of Portugal on April 26, 1821. For thirteen years, Rio de Janeiro, Brazil, functioned as the capital of the Kingdom of Portugal in what some historians call a metropolitan reversal (i.e., a colony exercising governance over the entirety of an empire). The period in which the court was located in Rio brought significant changes to the city and its residents, and can be interpreted through several perspectives.

It had profound impacts on Brazilian society, economics, infrastructure, and politics. The transfer of the king and the royal court "represented the first step toward Brazilian independence, since the king immediately opened the ports of Brazil to foreign shipping and turned the colonial capital into the seat of government."