Peter III (Portuguese: Pedro III) became King of the Kingdom of Portugal jure uxoris by the accession of his wife and niece Queen Maria I in 1777, and co-reigned alongside her until his death.
Pedro married his niece Maria, Princess of Brazil, in 1760, at which time she was the heiress presumptive to the throne then held by his brother José I. According to custom, Pedro thus became king of Portugal in right of his wife. They had six children, of whom the eldest surviving son succeeded Maria as João VI on her death in 1816.
Pedro made no attempt to participate in government affairs, spending his time hunting or in religious exercises.