Teixeira, Pedro (pĕˈdrŏ tāˈshārə) [key], d. 1640, Portuguese explorer, one of the early voyagers on the Amazon. He commanded the expedition sent by the governor of Maranhão up the Amazon in the autumn of 1637. He reached the upper Amazon early in 1638, discovering the Rio Negro, and in July he met an expedition under Pedro de Costa Favilla on the Napo. Later he reached Quito, then returned down the Amazon. He was accompanied on this return journey by the Jesuit priest Cristóbal de Acuña, who wrote an account of the voyage. He claimed the Napo for Portugal, at that time united with Spain through the king, Philip IV of Spain (Philip III of Portugal).