The Tennis Court Oath was important because it was the first step in the Third Estate of France forming an organized protest of the French government in the lead-up to the French Revolution. After arguments with the First and Second estates over their roles in the governing of France, a large group of members of the Third Estate met at a nearby tennis court and vowed to forge a new constitution that guaranteed more rights for commoners.
At the time of the Tennis Court Oath, France was a monarchy ruled by King Louis XVI. Under his rule, France formed a national assembly of citizens from different classes to work together to solve the dire financial situation of the country. The First Estate consisted of French nobles, the Second Estate consisted of clergy, and the Third Estate was comprised of commoners. Although these estates signaled a willingness to allow the populace a say in governing, the Third Estate was not granted voting privileges.
The Third Estate met to discuss their treatment, and King Louis XVI ordered them to disperse. In defiance, they stayed congregated on an indoor tennis court and made the Tennis Court Oath, in which they vowed to work together to change the French government. This group of commoners named themselves the National Assembly. They gradually became quite powerful. These events culminated in the outbreak of the French Revolution, and the beheading of King Louis XVI.