He was born Quobna Ottobah Cugoano in 1757 near Ajumako, in modern-day Ghana. He was a Fanti. His family was friends with the local chief.
At the age of 13, Cuguano was sold into slavery and transported to Grenada to work on an island plantation. He worked in the Lesser Antilles until he was purchased in 1772 by an English merchant, who took him to England. That year, the merchant had Cuguano baptized as John Stuart; he was given his freedom in England following the decision in the Somersett Case (1772), which ruled there was no basis for slavery in English common law.