The Alcyon was a French bicycle, automobile, and motorcycle manufacturer between 1903 and 1954.

Alcyon originated from about 1890 when Edmond Gentil started the manufacture of bicycles in Neuilly, Seine. In 1902, this was complemented by motorcycle production and in 1906, the first cars were shown at the "Salon de l'Automobile" in Paris, France. Also in 1906 it founded the professional Alcyon cycling team which was active until 1955, including winning the Tour de France 6 times.

In 1912 Alcyon competed at the Isle of Man TT races with a 348cc single-cylinder engine featuring two inlet valves and two exhaust valves. Both bikes failed to finish the Junior TT race.

Alcyon had local success in France during the 1920s, with riders such as Marc Jolly, Marcel Mourrier, Jean Durand and Lucien Lemasson winning races. During this time too, this bicycle brand got its nickname "l'intrépide Alcyon".

Two models were shown in 1906, one a two-seat light car with single-cylinder 950 cc engine and a larger four seat model with 1.4-litre four-cylinder engine. Both engines were bought in from Gentil. The cars were advanced models with 3-speed gearboxes and shaft drive. However, the single-cylinder models were dropped in 1912 and larger models of up to 2120 cc were added to the range. By then, most of the engines were obtained from Zurcher.

The company moved to Courbevoie, Seine in 1912.

In 1954 Peugeot absorbed Alcyon.

In 1914, the company's name was changed to Automobiles Alcyon. The first post-war model, released in 1921, was the 1914 cc four-cylinder model, some examples of which were tuned and sold by the Lyons agent, M. Giroux, as Alycon-GL (Giroux Lyons) and performed quite well in competition. However, the car was not a success and did not sell well, so in 1923, Alcyon moved into the production of cyclecars, using 500 cc two-stroke flat-twin engines in a design bought from SIMA-Violet. By 1929 Alcyon realised that the cyclecar era was over, and discontinued car production.