Amadeus William Grabau (January 9, 1870 – March 20, 1946) was an American geologist, teacher, stratigrapher, paleontologist, and author who worked in the United States and China.

Grabau, led a group of dissident Lutheran immigrants from Germany to Buffalo, New York.

The pro-German attitudes during World War I led to an estrangement from his wife, and in 1919 he left Columbia for China.

He traveled to China to become a professor at Peking University and a member of the Chinese Geological Survey in October 1920.

In 1936, the National Academy of Sciences awarded him the Mary Clark Thompson Medal from for most important service to geology and paleontology.