Cosimo III de' Medici, Grand Duke of Tuscany (14 August 1642 – 31 October 1723) was Grand Duke of Tuscany from 1670 to 1723.

He was the son of Grand Duke Ferdinando II and Vittoria della Rovere.

In 1661, he married Marguerite Louise d'Orléans, a cousin of the French King Louis XIV, but they separated in 1675. They had the following children:

• Ferdinando (1663-1713)
• Anna Maria Luisa (1667-1743), who married Johann Wilhelm, Elector Palatine (1658-1716).
• Gian Gastone (1671-1737), who succeeded his father as the last Medici Grand Duke of Tuscany in 1723.