Harrison "Jack" Schmitt (born July 3, 1935) is a geologist, astronaut, and former senator. He received a Bachelor of Science degree in science from the California Institute of Technology in 1957 and a Doctorate of Philosophy in geology from Harvard University in 1964.

He was a member of the Apollo 17 mission in 1972 and thereby the first and only geologist to land on the moon. Schmitt served for six years as a Republican United States Senator representing New Mexico, defeating incumbent Joseph Montoya in 1976. However, mainly due to his staunch support of the economic policies of his fellow Republican, President Ronald Reagan, Schmitt himself was defeated by Democrat Jeff Bingaman in 1982.