Alexis Anastay Julien (February 13, 1840 – May 7, 1919) was an American geologist who taught at Columbia University's School of Mines for many years.

[1] He graduated from Union College in 1859, but continued as a student in the chemical laboratory a year longer.

In 1860 he went to the guano island of Sombrero as resident chemist, and continued there until 1864, also making studies of its geology and natural history, especially of its birds and land shells.

He sent his collections to the Smithsonian Institution, for which he also made meteorological observations, this island being the most southerly under its direction.

In 1862 he made a geological survey of the islets around St. Bartholomew for the Swedish government, receiving in recognition of his services a gold medal from the king of Sweden.