Alexander Hollaender (9 December 1898 – 6 December 1986) was one of the world's leading researchers in radiation biology and in genetic mutations. In 1983 he was given the Enrico Fermi Award by the United States Department of Energy for his contributions in founding the science of radiation biology, and for his leadership in promoting "scientific exchanges" between American scientists and scientists from developing countries.

Hollaender was born in Samter, German Empire (Szamotuły, Poland), he emigrated to the US in 1921.In 1939 Hollaender published research showing that the mutations of spores of the ringworm fungus occurred in the same spectrum as the absorption spectrum of nucleic acids indicating that nucleic acids form the building blocks of genes. A young Esther M. Zimmer, who worked with Dr. Hollaender at the U. S. Public Health Service (Bethesda, MD), published with Dr. Hollaender, Eva Sansome and Milislav Demerec in this very early field of x-ray- and UV-induced mutations. Later on, Esther M. Zimmer (now Esther Lederberg) became one of the most influential founders of bacterial and bacteriophage (Lambda phage) genetics. Later on, Hollaender worked at Oak Ridge National Laboratories with M. Laurance Morse, who himself later went on to collaborate with Esther Lederberg.