Guillaume Bigourdan, French astronomer and academic (b. 1851)
Camille Guillaume Bigourdan (French pronunciation: ​[kamil gijom biguʁdɑ̃]; 6 April 1851 – 28 February 1932) was a French astronomer.

Bigourdan was born at Sistels, Tarn-et-Garonne to Pierre Bigourdan and Jeanne Carrière. In 1877 he was appointed by Félix Tisserand as assistant astronomer at the Toulouse Observatory, and in 1879 followed Tisserand to the Paris Observatory when the latter became director there.

He spent many years verifying the positions of 6380 nebulae. He hoped to set a basis for future studies of the proper motion of nebulae; this turned out to be more or less in vain, since distant nebulae will not show any proper motion. However, he did discover approximately 500 new objects.

In 1902 he participated in an effort to redetermine with greater precision the longitude difference between London and Paris. He became a member of the Bureau des Longitudes in 1903, and a member of the French Academy of Sciences in 1904.

He described a method for adjusting equatorial mount telescopes, which was known as "Bigourdan's method".

Bigourdan won the Lalande Prize of the French Academy of Sciences in 1883 and in 1891, the Valz Prize of the same institution in 1886, and the Gold Medal of the Royal Astronomical Society in 1919. He was director of the Bureau International de l'Heure from 1919 to 1928. In 1919, he received the Prix Jules Janssen, the highest award of the Société astronomique de France, the French astronomical society.

He married a daughter of Amédée Mouchez.