The Russell Sage Foundation is an American non-profit organisation established by Margaret Olivia Sage in 1907 for “the improvement of social and living conditions in the United States.” It was named after her recently deceased husband, railroad executive Russell Sage. The foundation dedicates itself to strengthening the methods, data, and theoretical core of the social sciences in order to better understand societal problems and develop informed responses. It supports visiting scholars in residence and publishes books and a journal under its own imprint. It also funds researchers at other institutions and supports programs intended to develop new generations of social scientists. The foundation focuses on labor markets, immigration and ethnicity, and social inequality in the United States, as well as behavioral economics.

Margaret Olivia Slocum Sage, known as Olivia Sage, was an American philanthropist known for her contributions to education and progressive causes. In 1869 she became the second wife of industrialist Russell Sage. At his death in 1906, she inherited a fortune estimated at more than $63,000,000, to be used at her discretion.