Robert Horace Baker (March 29, 1883, in Northampton, Massachusetts – June 23, 1964, in Upland, California) was an astronomer.

His graduate work in astronomy was done at the University of Pittsburgh where he was an assistant at Allegheny Observatory and where he obtained the Ph.D. degree in 1910.

In 1931–1932 and again in 1938–1939 he was a research associate of Harvard University while on sabbatical working with Bart Bok’s Star Count Circuit.

He was an exceptionally fine observer and possessed the added talent of clarity of style that made his articles models of scholarly writing.

His students include Elaine Nantkes, Lois Kiefer, David Heeschen, and Allan Sandage.

Otto Struve called An Introduction to Astronomy an excellent textbook that set a high standard.

Baker held this post until his retirement from the University of Illinois in 1951, where he had been an assistant dean of the graduate college in 1949–1951.