Martim Afonso de Sousa (c. 1500 – 21 July 1571) was a Portuguese fidalgo, explorer and colonial administrator. Born in Vila Viçosa, he was commander of the first official Portuguese expedition into mainland of the colony of Brazil. Threatened by the presence of French and Dutch ships along the coast of Brazil, the Portuguese crown in December 1530 sent a fleet with 400 people led by Martim Afonso de Sousa to establish control and explore. His mission was to place Portuguese markers as far south as the River Plate estuary, but he was shipwrecked there. He died in Lisbon in 1571.