Ohta, Tomoko (born September 7, 1933, Miyoshi, Aichi) is a Japanese scientist working on population genetics/molecular evolution. She graduated from the Agriculture Department of the University of Tokyo in 1956. She obtained her Ph.D. from North Carolina State University. Returning to Japan, she worked under Motoo Kimura. After working on the neutral theory of evolution with her mentor Kimura, she became convinced the importance of the mutations that were nearly neutral.

She developed the slightly deleterious model (Ohta, 1973), then a more general form, the nearly neutral theory of evolution.She worked at the Japanese National Institute of Genetics from 1969 to 1996,and, in 2002, she was elected to the United States National Academy of Sciences as a foreign associate in evolutionary biology.Ohta and Richard Lewontin were jointly awarded the Crafoord Prize for 2015 "for their pioneering analyses and fundamental contributions to the understanding of genetic polymorphism".