Alfred Ernst (21 February 1875, Winterthur – 17 September 1968, Zürich) was a Swiss botanist. He attended classes at the teachers' seminar in Küsnacht, followed by studies of biological sciences in Paris. From 1897 to 1899 he worked as a teacher in Naples. Afterwards, he received his doctorate in sciences from the University of Zürich, where in 1905, he became an associate professor. From 1909 to 1945 he was a professor of general botany at Zürich, being chosen university rector in 1928.