Y. Fongi, also Ypsilon Fongi, Yolanther Fongi, later Siddhartha Y Fongi, (* January 2, 1936 as Werner Gartung in Vechelde near Braunschweig; † May 13, 2012 in Zschachenmühle) was a versatile German avant-garde painter, draughtsman, musician, object and conceptual artist. An important representative of Critical Realism in art, Pop Art, Conceptual Art and Fluxus in the 1960s, he last lived in Zschachenmühle, Thuringia.