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.
His primary research dealt with the propagation of algae, the embryology of flowering plants and heterostyly in Primula species. In 1905/06 and 1930/31 he was involved in botanical investigations in Java.
