Richard C. Hoagland (born April 25, 1945) is an author who claims that advanced civilizations exist or once existed on the Moon, Mars and on some of the moons of Jupiter and Saturn, and that a number of conspiracies exist involving NASA and the United States government to keep these facts secret. As a non-scientist who is not subject to peer review, he is free to disagree with the body of knowledge represented by astronomy and planetary science — and he has done so emphatically, in books, videotapes, lectures, mass media interviews, and press conferences.