A. E. (Andrew Ellicott) Douglass (July 5, 1867, Windsor, Vermont – March 20, 1962, Tucson, Arizona) was an American astronomer. He discovered a correlation between tree rings and the sunspot cycle.
Douglass founded the discipline of dendrochronology, which is a method of dating wood by looking at the growth ring pattern. He started his discoveries in this field in 1894 when he was working at the Lowell Observatory. During this time he was an assistant to Percival Lowell and William Henry Pickering, but had a falling-out with them, when his experiments made him doubt the existence of artificial "canals" on Mars and visible cusps on Venus
Craters on the Moon and Mars are named in his honor.