The location where the Battle of Fontenoy was fought is located in what is now Belgium.
The Battle of Fontenoy was one of the most important battles of the War of the Austrian Succession. The major cause of the war was the question of whether Maria Theresa, as a woman, has the right to inherit the numerous Habsburg estates from her father Charles VI, who died without male issue. Many countries (e.g. France, Prussia, and Bavaria) denied Maria her right to inherit these lands, while the British supported her.
The War of the Austrian succession was fought on many battlefields throughout Europe, from Silesia to what in now Belgium, and even encompassed the European colonies in North America, the Caribbean and India. The Battle of Fontenoy was probably the most important individual battle of that war, and took place near the current Belgian-French border, specifically near the village of Fontenoy near the city of Tournai. That region used to belong to the Habsburgs, and was called the Austrian Netherlands.
More than 100,000 soldiers participated in the battle, with both armies being roughly equal in size. The leader of the Habsburg army was the young Duke of Cumberland, son of British king George II from the Hanover dynasty. The Austrian contingent was commanded by the much more experience Field Marshal Count Lothar Joseph Dominik von Königsegg-Rothenfels, but he was subordinate to the British commander.
French king Louis XV was personally present near the battlefield and nominally the supreme commander of the French side. The de facto French commander was Maurice de Saxe, an experienced and competent commander who managed to achieve a great victory after which most of the Austrian Netherlands fell under French dominion. In recognition of his skill, the French king awarded him the royal Château de Chambord in the Loire valley after the battle.