Brazil gained independence from Portugal in 1822. The decisive declaration came on 7 September, when Prince Pedro proclaimed independence beside the Ipiranga Brook near São Paulo, an event remembered as the Cry of Ipiranga.
The break followed growing tension between Brazil and Portugal. After Napoleon’s invasion of Portugal in 1807, the Portuguese royal court moved to Rio de Janeiro, and Brazil’s political and economic importance increased. When the court later tried to restore Brazil to a more subordinate colonial role, Pedro refused orders to return to Portugal and supported Brazilian autonomy.
Independence did not instantly end the conflict. Fighting continued in several provinces, including Bahia, Maranhão, Pará, and Piauí, where Portuguese forces still held power. Pedro was acclaimed Emperor Pedro I in October 1822, while Portugal formally recognized Brazilian independence through the Treaty of Rio de Janeiro in 1825. That later date is a common mix-up, but 1822 is the year of the declaration and the accepted answer to this question.