Duarte Fernandes (16th century) was a Portuguese diplomat and the first European to establish diplomatic relations with Thailand, when in 1511 he led a diplomatic mission to Ayutthaya Kingdom (Kingdom of Siam), after the Portuguese conquest of Malacca.
Duarte Fernandes was a tailor who went to Malacca in the first expedition of Diogo Lopes de Sequeira in September 1509. In the sequence of a failed plot to destroy the expedition, he was among nineteen Portuguese that stood arrested in Malacca, together with Rui de Araújo, having gathered knowledge about the culture of the region.
In 1511, soon after the Portuguese conquest of Malacca, knowing of Siamese ambitions over Malay, Afonso de Albuquerque immediately sent him in a diplomatic mission to the court of the King of Siam Ramathibodi II, traveling in a Chinese junk returning home. There he was the first European to arrive, establishing amicable relations between the Kingdom of Portugal and the Kingdom of Siam, returning with a Siamese envoy with gifts and letters to Albuquerque and the king of Portugal. Five years after that initial contact, Ayutthaya and Portugal concluded a treaty granting the Portuguese permission to trade in the kingdom.
- Manuel Teixeira, The Portuguese missions in Malacca and Singapore (1511-1958), Agência Geral do Ultramar, 1963 pp. 38, 54
- Asian review, Volume 13 by Čhulālongkō̜nmahāwitthayālai. Sathāban ʻĒchīasưksā, p.39
- Donald Frederick Lach, Edwin J. Van Kley, "Asia in the making of Europe", pp. 520-521, University of Chicago Press, 1994, ISBN 978-0-226-46731-3