John Venn’s diagram, 1880
John Venn published it in July 1880, in the Philosophical Magazine, in a paper on the diagrammatic and mechanical representation of propositions and reasonings. Three circles for three classes, overlapping so that every combination has a region of its own. He shaded the regions a proposition ruled out.
Venn himself called them Eulerian circles. Clarence Irving Lewis called them Venn diagrams in 1918, and that stuck.