Don Juan de Mendoza y Luna, 3rd Marquis of Montesclaros (Spanish: Juan de Mendoza y Luna, marqués de Montesclaros, or sometimes marqués de Montes Claros) (January, 1571, Guadalajara, Spain – October 9, 1628, Madrid), Spanish nobleman, man of letters, and the tenth viceroy of New Spain. He governed from October 27, 1603 to July 2, 1607. Thereafter he was viceroy of Peru, from December 21, 1607 to December 18, 1615. After returning to Spain, he became advisor to the king and a high official in the Court.
Juan de Mendoza y Luna was the posthumous son of the second Marqués de Montesclaros. He was raised by his mother, Isabel Manrique de Padilla.
He served with distinction in the army of the Duke of Alba in the Portuguese campaign, as a captain of lancers. For his service, he was awarded the Order of Caballero de Santiago in 1591. Later he was governor of Seville, where he first became acquainted with the affairs of the Indies. On May 19, 1603 the Crown named him viceroy of New Spain.