The siege of Mons took place between 19 September and 23 October 1709 during the War of the Spanish Succession. It saw a Franco-Spanish garrison in the fortified town of Mons, then in the Spanish Netherlands, besieged by a force of the Duke of Marlborough's Grand Alliance army under the command of the Prince of Orange.

John William Friso became the (titular) Prince of Orange in 1702. He was the Stadtholder of Friesland and Groningen in the Dutch Republic until his death by accidental drowning in the Hollands Diep in 1711. From 1938 to 2022, Friso and his wife, Marie Louise, were the most recent common ancestors of all then-reigning European monarchs. As of 2023, the most recent common ancestors of all currently-reigning European monarchs are Louis IX, Landgrave of Hesse-Darmstadt and his wife Countess Palatine Caroline of Zweibrücken.