Erwin Baur (16 April 1875, in Ichenheim, Grand Duchy of Baden – 2 December 1933) was a German geneticist and botanist.
He was director of the Kaiser Wilhelm Institute for Breeding Research (then in Müncheberg, now in Cologne, and since 1938 the Erwin Baur-Institute).
In 1909 working on the chloroplast genes in Pelargonium (geraniums) he showed that they violated four of Mendel's five laws.
Baur stated that Since the 1930s and the work of Otto Renner, plastid inheritance became a widely accepted genetic theory.
In 1921 and 1932, together with Fritz Lenz and Eugen Fischer, Baur coauthored two volumes that became the book Menschliche Erblichkeitslehre (Human Heredity), which was a major influence on the racial theories of Adolf Hitler.