He was born in Viseu on 31 October 1391 and died in Tomar on 9 September 1438. Son of king D. João I and queen D. Filipa de Lencastre, on the death of his older brother Afonso, he became heir to the Portuguese Crown.
D. Duarte was named after his mother’s grandfather, king D. Edward III of England. From a very young age, D. Duarte accompanied his father in the affairs of the kingdom, and was thus an heir prepared to reign; in 1412 he was formally associated with the governance by his father, having the affairs of justice and finance.
He was a cultured man, with a love for literature, possessing a rich library and with a wide knowledge of the classical authors and the doctrines of the Church, as evidenced by his book “O Leal Conselheiro”. He also composed “A Arte de Bem Cavalgar Toda a Sela”.
D. Duarte ordered the compilation of all the kingdom’s legislation, which would only be finished during the reign of D. Afonso V, hence its name, Ordenações Afonsinas.
D. Duarte continued the policy of encouraging both maritime exploration and the conquests in Africa.
Outside the political sphere, D. Duarte was a man interested in culture and knowledge and wrote books of poetry and prose.