Robert Sinclair Dietz (September 14, 1914 – May 19, 1995) was an American scientist with the United States Coast and Geodetic Survey.

Dietz, born in Westfield, New Jersey,[1] was a marine geologist, geophysicist and oceanographer who conducted pioneering research along with Harry Hammond Hess concerning seafloor spreading, published as early as 1960–1961.

Dietz was an outspoken critic of creationism, and was the faculty advisor of two student groups at Arizona State University in 1985, Americans Promoting Evolution Science (APES) and the Phoenix Skeptics.

Dietz spoke on evolution and creationism at meetings of these groups,[5] and debated creationist Walter Brown and Christian apologist William Lane Craig at Arizona State University.

[6] The ASU School of Earth and Space Exploration sponsors annual Robert S. Dietz Memorial Public Lectures, which have been given by: