John VI (1769–1826), early-19th-century king of Portugal. He became regent in 1792 when his mother, Maria I, was judged mentally unfit to rule. He fled to Brazil in 1807 when an invasion by Napoleon was feared. In 1816, while still in Brazil, John became Portugal's king, but he didn't return until a revolution in his favor 5 years later. In 1822 his son, Pedro I, declared Brazil independent.