Athelstan Frederick Spilhaus (November 25, 1911 – March 30, 1998) was a South African-American geophysicist and oceanographer. He was born in Cape Town, South Africa. He became a US citizen in 1946. Among other accomplishments, Spilhaus is credited with proposing the establishment of Sea Grant Colleges at a meeting of the American Fisheries Society in 1963 as a parallel to the successful land-grant colleges, which he claimed was "one of the best investments this nation ever made. The same kind of imagination and foresight should be applied to the exploration of the sea."
In 1936 Spilhaus joined the Woods Hole Oceanographic Institution in Massachusetts, where he developed the bathythermograph, which made the measurement of ocean depths and temperatures from a moving vessel possible, a device which proved indispensable to submarine warfare. This invention established his international reputation.
Later he became Dean of the University of Minnesota's Institute of Technology.
Spilhaus was the founder and original planner of the Minnesota Experimental City.
Spilhaus was also chair of the scientific advisory committee of the American Newspaper Publishers Association. He became known by the public for his Our New Age Sunday feature, which appeared in the color comics section of 93 newspapers (1957–1973). The strip therefore was quite influential in its time and John F. Kennedy is cited to have said on a meeting with Spilhaus in 1962: "The only science I ever learned was from your comic strip in the Boston Globe." He apparently enjoyed authoring the feature; in response to a question about its broad scope in a mid-sixties TV interview, Spilhaus modestly replied he'd learned quite a lot by writing it.
He also served on the board of trustees of Science Service, now known as Society for Science & the Public, from 1965 to 1978.