The Montgolfier brothers – Joseph-Michel Montgolfier (French: [ʒozɛf miʃɛl mɔ̃ɡɔlfje]; 26 August 1740 – 26 June 1810) and Jacques-Étienne Montgolfier ([ʒak etjɛn mɔ̃ɡɔlfje]; 6 January 1745 – 2 August 1799) – were aviation pioneers, balloonists and paper manufacturers from the commune Annonay in Ardèche, France. They invented the Montgolfière-style hot air balloon, globe aérostatique, which launched the first confirmed piloted ascent by humans in 1783, carrying Jacques-Étienne.

Joseph-Michel also invented the self-acting hydraulic ram (1796) and Jacques-Étienne founded the first paper-making vocational school. Together, the brothers invented a process to manufacture transparent paper.

Joseph-Michel and Jacques-Étienne Montgolfier were born into a family of paper manufacturers. Their parents were Pierre Montgolfier (1700–1793) and Anne Duret (1701–1760), who had 16 children. Pierre Montgolfier established his eldest son, Raymond (1730–1772), as his successor.^{[citation needed]}

Joseph-Michel was the 12th child. Described^{[by whom?]} as a maverick and dreamer, he was impractical in terms of business and personal affairs. Étienne was the 15th child, had a much more even and businesslike temperament and was sent to Paris to train as an architect. After the sudden and unexpected death of Raymond in 1772, he was recalled to Annonay to run the family business. In the subsequent 10 years, Étienne applied his talent for technical innovation to the family business of paper making, which then as now was a high-tech industry. He succeeded in incorporating the latest Dutch innovations of the day into the family mills.^{[citation needed]}

Of the two brothers, it was Joseph who was first interested in aeronautics; as early as 1775 he built parachutes, and once jumped from the family house. He first contemplated building machines when he observed laundry drying over a fire incidentally form pockets that billowed upwards. Joseph made his first definitive experiments in November 1782 while living in Avignon. He reported some years later that he was watching a fire one evening while contemplating one of the great military issues of the day—an assault on the fortress of Gibraltar, which had proved impregnable from both sea and land. Joseph mused on the possibility of an air assault using troops lifted by the same force that was lifting the embers from the fire. He believed that the smoke itself was the buoyant part and contained within it a special gas, which he called "Montgolfier Gas", with a special property he called levity, which is why he preferred smoldering fuel.

Joseph then built a box-like chamber 0.9 by 0.9 by 1.2 metres (3 ft × 3 ft × 4 ft) out of very thin wood, and covered the sides and top with lightweight taffeta cloth. He crumpled and lit some paper under the bottom of the box. The contraption quickly lifted off its stand and collided with the ceiling.

Joseph recruited his brother to balloon building by writing, "Get in a supply of taffeta and of cordage, quickly, and you will see one of the most astonishing sights in the world." The two brothers built a similar device, three times larger having a volume 27 times greater. On 14 December 1782 they conducted their first test flight, using ignited wool and hay as fuel. The lifting force was so great that they lost control of their craft. The device floated nearly two kilometers (1.2 mi) but was destroyed after landing by the "indiscretion" of a bypasser.

To make a public demonstration and to claim its invention, the brothers constructed a globe-shaped balloon of sackcloth tightened with three thin layers of paper inside. The envelope could contain nearly 790 m³ (28,000 cu ft) of air and weighed 225 kg (496 lb). It was constructed of four pieces (the dome and three lateral bands) and held together by 1,800 buttons. A reinforcing fish net of cord covered the outside of the envelope.