Jean Cabannes (b. Marseille August 12, 1885 - d. Saint-Cyr-sur-Mer October 31, 1959) was a French physicist specialising in optics.

From 1910 to 1914 Cabannes worked in the laboratory of Charles Fabry in Marseille on the topic launched by Lord Rayleigh at the end of the 19th century of how gas molecules diffused light. In 1914 he showed that pure gases could scatter light. This was published in Comptes Rendus in 1915. His career was then interrupted for five years by World War I.

In 1919 Cabannes returned to Fabry's laboratory to complete his thesis, after which he moved to Montpellier, and later on to Paris. In 1925 he and Jean Dufay calculated the height of the ozone layer. J. Cabannes, P. Daure and Y. Rocard were among the scientists who, in 1928, discovered that gases diffusing monochromatic light could also change their wavelength (the Cabannes - Daure effect).

This was identified independently by C.V. Raman and K.S. Krishnan in liquids, and by G.S. Landsberg and L.I. Mandelstam in crystals. Cabannes was among the candidates for the Nobel Prize in Physics of 1929 (proposed by C. Fabry), which was awarded to de Broglie.

The 1930 prize went to Raman who gave the complete explanation of the effect now bearing his name, using quantum mechanics.

The lunar crater Cabannes was named after him.