Abbott Handerson Thayer (August 12, 1849 – May 29, 1921) was an American artist, naturalist and teacher. As a painter of portraits, figures, animals and landscapes, he enjoyed a certain prominence during his lifetime, as shown by the fact that his paintings are in the most important U.S. art collections. In the last third of his life, he worked together with his son, Gerald Handerson Thayer, on a major book about protective coloration in nature, titled Concealing Coloration in the Animal Kingdom: An Exposition of the Laws of Disguise Through Color and Pattern; Being a Summary of Abbott H. Thayer’s Disclosures. First published by Macmillan in 1909, then reissued in 1918, it had a widespread impact on the use of military camouflage during World War I. He also influenced American art through his efforts as a teacher, taking on apprentices in his New Hampshire studio.

Thayer was born in Boston, Massachusetts. The son of a country doctor, his childhood was spent in rural New Hampshire, near Keene, at the foot of Mount Monadnock. In that rural setting, he became an amateur naturalist (in his own words, he was “bird crazy”), a hunter and a trapper. He studied Audubon's Birds of America on an almost daily basis, experimented with taxidermy, and made his first artworks: watercolor paintings of animals.

At age 18, he moved to Brooklyn, New York, to study painting at the Brooklyn Art School and the National Academy of Design. In 1875, having married Kate Bloede, he moved to Paris, where he studied for four years at the École des Beaux-Arts, with Henri Lehmann and Jean-Léon Gérome, and where his closest friend became the American artist George de Forest Brush. Returning to New York, he set up his own portrait studio (which he shared with Daniel Chester French), became active in the Society of American Painters, and began to take in apprentices.