Isaac Jacob Schoenberg (April 21, 1903 – February 21, 1990) was a Romanian-American mathematician, known for his invention of splines.

From 1922 to 1925 he studied at the Universities of Berlin and Göttingen, working on a topic in analytic number theory suggested by Issai Schur.

In Göttingen, he met Edmund Landau, who arranged a visit for Schoenberg to the Hebrew University of Jerusalem in 1928.

In 1930, he was awarded a Rockefeller Fellowship, which enabled him to go to the United States, visiting the University of Chicago, Harvard, and the Institute for Advanced Study in Princeton, New Jersey.

His coauthors included John von Neumann, Hans Rademacher, Theodore Motzkin, George Polya, A. S. Besicovitch, Gábor Szegő, Donald J. Newman, Richard Askey, Bernard Epstein and Carl de Boor.