William David McElroy (22 January 1917 – 17 February 1999) was an American biochemist and academic administrator.

He initiated an independent research program in bioluminescence, recruiting students to collect fireflies to perform experiments.

In collaboration with H. Bentley Glass he edited several symposium volumes, including The chemical basis of heredity,[2] with authors including François Jacob, Erwin Chargaff, Severo Ochoa, Arthur Kornberg, Max Delbrück and Francis Crick.

The contributors are ... of the very highest standard ... Workers in the large field of chromosomes, genes, nucleic acids and viruses will find the book essential.He was awarded the Howard N. Potts Medal in 1971.

He was first married to Nella Amelia Winch in 1940 with whom he had four children; Ann, Mary, Thomas and William, Jr. His second marriage was in 1967 to biochemist Marlene Anderegg DeLuca.