Katherine Greacen Nelson (December 9, 1913 – December 29, 1982), born in Sierra Madre, California, was an American geologist.
She was one of the first women to receive a degree in geology, obtaining a PhD from Rutgers University.
Growing up in a military family exposed to nature and traveling at an early age, Nelson showed an eagerness for geology by devoting her days to learning the various geological processes that encompass the earth, eventually winning a prize for an excellence in geology from Vassar College.
She was later hired by Milwaukee-Downer College as part of college's expanding geological and geographical sciences department eventually leaving her position in 1943 to help as a petroleum geologist as part of the war effort.
Nelson went on to give many lectures that helped inspire students of all genders towards the field of geography and geology.
She died in December 1982 at the age of 69 in Milwaukee, Wisconsin after a long battle with cancer.