The Montgolfier brothers publicly demonstrated their hot-air balloon in Annonay, France, on 4 June 1783.
Joseph-Michel and Jacques-Étienne Montgolfier built a large paper-and-linen balloon and inflated it with hot air produced by burning material beneath the opening. The unmanned demonstration rose dramatically before a crowd, showing that heated air could lift a substantial fabric envelope.
This event came months before the first human flights. The Annonay demonstration is often confused with the later Versailles flight carrying animals or the first free human flight from Paris. Those were separate milestones in the rapid development of ballooning during 1783.
The Montgolfiers did not understand buoyancy in modern scientific terms, and they initially believed a special smoke-filled gas helped the balloon rise. Nevertheless, their practical experiments established the basic principle used by hot-air balloons today: warm air inside the envelope is less dense than cooler air outside it.