The First Reign was the period of Brazilian history in which Pedro I ruled Brazil as Emperor. It began on September 7, 1822, when Brazil's independence was proclaimed, and ended on April 7, 1831, when Pedro I abdicated the Brazilian throne.

When Pedro I declared independence, defeating those who were still loyal to Portugal, he achieved great prestige and power. In 1823, he convened the Constituent Assembly which, amid great disagreements between parliamentarians and the Emperor, was dissolved in the Night of Agony. The emperor then convened a Council of State to draft Brazil's first constitution, which was enacted the following year. The document brought centralizing aspects along with the controversial moderating power, which contributed to growing discontent and revolts, including the outcome of the Cisplatine War and the assassination of Líbero Badaró, a well-known journalist. These incidents diminished the emperor's popularity and led to incidents such as a trip to Minas Gerais, where Pedro I was harassed by the locals.

At this point, two of the most important groups supporting the emperor also withdrew their support: the nobility and the army. This made the political situation untenable; confronted, Pedro I found no solution and, in April 1831, abdicated in favor of his son, Pedro de Alcântara, then 5 years old.

This period of transition was marked by a major economic, financial, social and political crisis. It is historically incorrect to refer to this period as the "First Empire", since Brazil had a single continuous imperial period, divided into the First Reign, the Regency Period and the Second Reign.

After Napoleon Bonaparte declared war on England's allies, he ordered an invasion of Portugal, which had refused to comply with the French demands regarding the continental blockade. For this reason, the British crown financed the arrival of the Portuguese Royal Family in Rio de Janeiro in 1808. After a few years living in the colony, John VI became king of the country, founding the United Kingdom of Portugal, Brazil and the Algarves on December 16, 1815; Rio de Janeiro was named the capital of the United Kingdom.

Under this new political status, Brazil experienced some conditions not seen before, such as the installation of some small industries in Rio de Janeiro and trade with countries other than Portugal. One of these countries was England, which benefited greatly from the political change, since it wouldn't have to wait for Brazilian products (raw materials, gold, minerals) to pass through Portugal first. For helping the Portuguese crown, the British signed two treaties with them, the Strangford Treaty (1810) and the Treaty of Alliance and Friendship (1810), which established the payment of only 15% in taxes, while the Portuguese paid 16% and the rest of the European countries 24%.

In 1820, the Portuguese population demanded the return of King John VI to Lisbon, as Napoleon had already been deposed in France. On August 24 of the same year, the Liberal Revolution broke out, first in the city of Porto and then in other Portuguese metropolises. Despite managing to postpone it for a few months, John VI was forced to return to Lisbon in 1822.

Pernambuco was the first Brazilian province to secede from the Kingdom of Portugal, eleven months before the proclamation of Brazil's independence. On August 29, 1821, an armed movement began against the government of Captain General Luís do Rego Barreto – the leader of the Pernambucan revolt – culminating in the formation of the Junta de Goiana. On October 5, the Portuguese troops surrendered and were expelled from Pernambuco in a movement known as the Beberibe Convention, considered to be the first episode of Brazilian independence.