Lyman Spitzer (b. June 26, 1914, Toldedo, OH-d. March 31, 1997, Princeton, NJ) was an American theoretical physicist, astronomer, and mountaineer. As a scientist, he carried out research into star formation, plasma physics, and in 1946, conceived the idea of telescopes operating in outer space. Spitzer invented the stellarator plasma device and is the namesake of NASA's Spitzer Space Telescope. He also was the founding director of Project Matterhorn, Princeton University's pioneering program in controlled thermonuclear research, renamed in 1961 as Princeton Plasma Physics Laboratory. As a mountaineer, he made the first ascent of Mount Thor, with Donald C. Morton.