Clément Ader (February 4 1841 – March 5 1926) was a French engineer born in Muret, Haute Garonne remembered primarily for his pioneering work in aviation.

In his time an electrical and mechanical genius, the engineer Ader innovated in a number of domains. He originally studied electrical engineering, and in 1878 improved the telephone, recently invented by Alexander Graham Bell. He refined the invention and established the first telephone network in Paris in 1880. In 1881, he invented the theater-phone, a system of telephonic transmission where two channels allowed binaural hearing and gave listeners an exact idea of the respective positions of the actors on a set; it was this invention which gave the first transmission in stereo of the spectacles of the Opera, over a distance of 2 miles (3 km) (1881).

Following this, he turned to mechanical flight and concentrated all of his time and money on it until the end of his life. Using the studies of Louis Mouillard (1834-1837) on the flight of birds, he constructed his first flying machine in 1886, the Éole. It was a bat-like design run by a lightweight steam engine of his own invention (4 cylinders developing 20 horsepower (15 kW). The weight was no more than 7 pounds per horsepower (4 g/W)), and it drove a four-blade propeller. The wings, with a span of 14 yards, were equipped with a system of warping and all together weighed 650 pounds (300 kg). On October 9, 1890, Ader attempted a flight the Éole, which succeeded in taking off and flying a distance of approximately 50m before witnesses. However, the plane then crashed and was wrecked.

Following the wreck of the Éole, Ader undertook the construction of an aircraft he called the Avion II (also referred to as the Zephyr or Éole II). Most sources agree that work on this aircraft was never completed, and it was abandoned in favour of the Avion III, However, Ader claimed in later life that he flew the Avion II in August 1892 for a distance of 200 yards (200 m) in Satory.

Ader's progress attracted the interest of the minister of war, Charles de Freycinet.

With the backing of the French War office, Ader developed and constructed the Avion III. It was like an enormous bat of linen and wood, with a 16-yard wingspan, equipped with two puller propellers of four blades, each powered by a steam engine of 30 hp (22 kW). After extensive taxi tests, Ader attempted a flight at Satory on October 14, 1897. Some witnesses contend that the Avion rolled, took off towards the sky and, before the official commission, flew a distance of more than 300 yards (300 m), while others contend that the Avion III crashed before even taking off. In any event, the commission was not impressed and withdrew its funding, but kept the results secret. After the Wright brothers made their flight, the commission released reports on Ader's flights, stating that they were successful.

Abandoning everything, and in particular public demonstrations, the "father of aviation" died in Toulouse in obscurity. His Avion is still displayed at the museum of the Conservatory of Arts and Industry in Paris. Non-French aviation historians often discredit any claims of priority, since all flights ended in crashes, many were disputed, and Ader greatly exaggerated his achievements in later life. Nonetheless, Ader's October 9, 1890 flight of the Éole remains relatively undisputed, and Ader is still admired for his efforts. In 1938, France issued a postage stamp honoring him, and Airbus named one of its aircraft assembly sites in Toulouse after him.de:Clément Ader es:Clément Ader fr:Clément Ader gl:Clément Ader nl:Clément Ader zh:克雷芒·阿德尔