Milislav Demerec (January 11, 1895 – April 12, 1966) was a Croatian-American geneticist, and the director of the Department of Genetics, Carnegie Institution of Washington [CIW], now Cold Spring Harbor Laboratory (CSHL) from 1941 to 1960, recruiting Barbara McClintock and Alfred Hershey.
He completed his PhD in 1923 and took up a research position at the Carnegie Institution of Washington's [CIW] Department of Genetics, now Cold Spring Harbor Laboratory.
After overcoming opposition from Thomas Hunt Morgan, Demerec oversaw the completion of much of the late Calvin Bridges’s work.
Demerec appointed Katherine Brehme Warren to complete The Mutants of Drosophila melanogaster (1944) and the book became a classic in the field.
In the 1950s he served on the genetics panel of the National Academy of Sciences' Committee on the Biological Effects of Atomic Radiation.