Siegfried Fred Singer, commonly known as S. Fred Singer, was an Austrian-born American physicist and atmospheric scientist (born September 27, 1924, in Vienna, Austria; died April 6, 2020). He earned a Bachelor of Electrical Engineering from Ohio State University (1943) and a Ph.D. in physics from Princeton University (1948). His early career involved significant contributions to space science and atmospheric research, including rocket instrumentation work during World War II. He held numerous prestigious positions, including Professor of Environmental Sciences at the University of Virginia (1971-1994, later emeritus), Chief Scientist at the Department of Transportation (1987-1989), and was an elected Fellow of major scientific organizations. In 1990, he founded the Science & Environmental Policy Project (SEPP), a nonprofit think tank. Singer became particularly known as a prominent climate change skeptic and for his contrarian views on several environmental and health issues, including stratospheric ozone depletion, UV-B exposure and melanoma, and passive smoking risks. He served as co-chair of the Heartland Institute's Nongovernmental International Panel on Climate Change (NIPCC). His positions led to affiliations with conservative think tanks and frequent media appearances challenging mainstream environmental science, creating a legacy marked by both pioneering space research and polarizing debates in environmental policy.