Rupprecht Geiger (1908 – 2009) was a German abstract painter and sculptor known for monochrome works and color-field paintings. For a time he concentrated almost exclusively on red, and his work matters for its focus on color as the subject of painting itself.
The only child of the painter Willi Geiger, he began painting on family trips to Spain, Morocco and the Canary Islands. From 1926 to 1935 he studied and taught architecture and art at academies in Munich, and from 1936 to 1940 he worked as an architect. He was drafted into World War II, fought on the Eastern Front in Poland and Russia, and in 1943 and 1944 worked as a war illustrator. His first exhibition of abstract painting came in 1948.
After the war he returned to architecture until 1962. In 1949 he co-founded the artists' group ZEN 49, and Hilla von Rebay chose to show his work at the Guggenheim Foundation. From 1965 to 1976 he was professor of painting at the Düsseldorf Academy of Fine Arts.
His paintings feature simple geometric forms such as rectangles, ovals and circles, bright colors and strong contrasts. In the 1950s he studied red in particular. Four editions of documenta in Kassel included his work, and a collection of his pieces is held by the Diozesanmuseum in Freising, near Munich.