Cosimo III de' Medici (14 August 1642 – 31 October 1723) was the sixth and penultimate Medici Grand Duke of Tuscany. He reigned from 1670 to 1723, and was the elder son of Grand Duke Ferdinando II. Cosimo's 53-year-long reign, the longest in Tuscan history, was marked by a series of laws that regulated prostitution and May celebrations. His reign also witnessed Tuscany's deterioration to previously unknown economic lows. He was succeeded by his elder surviving son, Gian Gastone, when he died, in 1723.