The Rio Branco law (Portuguese: Lei Rio Branco), also known as the Law of Free Birth (Lei do Ventre Livre), named after its champion, prime minister José Paranhos, Viscount of Rio Branco, was passed by the General Assembly of the Empire of Brazil on 28 September 1871.

However, children of enslaved women in Brazil were obligated to serve their mother's owners until the age of 21, a condition that was often more or less that of slavery.

[1] The law was the beginning of an abolition movement in Brazil, but it turned out to be more of a legal loophole than a radical measure that led to viable progress.

This law had more of an influence in the northern part of the country, which was leaning further toward wage rather than slave labor.

Many of those freed under the Rio Branco law migrated to the north to work for wages on the plantations.