Leo George Hertlein (1898 - 1972) was an American paleontologist and malacologist who studied the Recent and fossil mollusks of the eastern Pacific Ocean.
Hertlein was born on a farm in Pratt County, Kansas. After graduating high school in Wichita, Kansas, he moved to the West Coast and entered the University of Oregon as a geology major.
After graduating with a B.A., Hertlein enrolled as a graduate student at Stanford University. He received his doctorate in 1929. His dissertation was on the Pliocene fossils of the San Diego, California area.
In 1929, Hertlein was appointed assistant curator of the Department of Paleontology at the California Academy of Sciences. He rose to become the curator of Invertebrate Paleontology and elected a Fellow.
In the 1930s, he traveled to the Galapagos Islands and the nearshore areas of Central America and Mexico.
He published over 150 papers on Recent and fossil mollusks, echinoderms, and brachiopods from California, Oregon, Washington, and Mexico.
On many occasions, Hertlein worked with Ulysses S. Grant IV, who was a classmate at Stanford and who also worked on the fossil mollusks of California. They collaborated on several papers.