Thomas Barbour Lathrop (1847 – May 17, 1927) was an American philanthropist and world traveler. He was born in Alexandria, Virginia.
Lathrop was a grandson of Governor James Barbour of Virginia. He studied at the University of Bonn and Harvard University. Around 1890, he inherited a sizable fortune from his father.
As a young man, he had been a reporter for the newspaper San Francisco Morning Call. Although he spent much of his time traveling, Lathrop considered the Bohemian Club in San Francisco his home for the rest of his life.
After he became wealthy, Lathrop traveled around the world many times. In the 1890s, Lathrop met a young biologist named David Fairchild who he persuaded to become a plant explorer. He financed Fairchild and accompanied him on some of his early travels. Lathrop's travels with Fairchild are described in detail the Fairchild and Douglas books.