Louis XVII of France was the son of Louis XVI and Marie Antoinette. He was the Dauphin of France from 1793 until his death in 1795. He was the last monarch of the House of Bourbon and the last King of France before the French Revolution.
From Wikipedia
Louis XVII was the younger son of King Louis XVI of France and Queen Marie Antoinette. His older brother, Louis Joseph, Dauphin of France, died in June 1789, a little over a month before the start of the French Revolution. At his brother's death he became the new Dauphin, a title he held until 1791, when the new constitution accorded the heir apparent the title of Prince Royal.