The Marquessate of the Valley of Oaxaca () is a hereditary marquessal title in the Spanish nobility and a former seignorial estate in New Spain. It was granted to Don Hernán Cortés, "conquistador" who led the conquest of the Aztec Empire, by Charles V, Holy Roman Emperor in 1529. Despite its name, the marquessate covered a much larger area than the Valley of Oaxaca, comprising a vast stretch of land in the present-day Mexican states of Oaxaca, Morelos, Veracruz, Michoacán and Mexico.