Robert James Blattner (born 1931) was an emeritus mathematics professor at UCLA working on harmonic analysis, representation theory, and geometric quantization, who introduced Blattner's conjecture. Born in Milwaukee, Blattner received his Ph.D. from the University of Chicago in 1957.
Blattner was a visiting scholar at the Institute for Advanced Study in 1964-65. In 2012 he became a fellow of the American Mathematical Society.