Dorothy Swaine Thomas (October 24, 1899 – May 1, 1977) was an American sociologist and economist.
Between 1924 and 1948, Thomas held research and teaching positions at various institutions in the United States and Europe, including at the University of California, Berkeley, Columbia Teachers College, the Federal Reserve Bank in New York and the Institute of Social Science at the University of Stockholm.
Her students there included Ann R. Miller, also associated for many years with the Population Studies Center.
Thomas' main field of research was population growth, in particular the statistical side thereof.
She wrote a multi-volume work with Simon Kuznets on the development of population and economy of the United States.