Joao (also Juan, Jean) de Loureiro, Portuguese missionary, botanist and medical practitioner, became a member of the Society of Jesus (a Jesuit) in 1732. In 1742 he left Portugal for the Far East. On his way there he visited Mozambique, where he collected plants. Some of his specimens are in herbaria in Lisbon, Paris and London.
De Loureiro practised medicine in Cochin China (the southern part of Vietnam) and studied its flora until December 1777, when he moved to China. He also studied the flora of Cambodia. After returning to Europe in 1781 he published his two-volume Flora Cochinchinensis in 1790, containing descriptions of many new plant genera. Several botanical papers by him, and others on animal fossils and his astronomical observations, were published in the Memorias de Physica e de Mathematica da Academia de Lisboa.