Olaf Helliesen Lange (11 February 1875 – 19 April 1965) was a Norwegian painter and graphic designer.
Olaf Lange was born in Stavanger, in the county of Rogaland, Norway. He was the son of doctor Emil Lange (1821–1904) and Marie Helliesen (1840–1916). He studied in Paris at the Académie Julian in 1897 and Oslo. While living in Munich, he made friends with textile artist Frida Hansen, painter Kitty Kielland, and author Alexander Kielland. He died in Stavanger in 1965.
Olaf Lange is best known for his symbolistic paintings which are closely linked to the continental art nouveau style. He won appreciation especially for their color etchings with historical or literary themes. Olaf Lange gave a great deal of his work as a testament gift to Stavanger Faste Galleri, now Rogaland Kunstmuseum and the British Museum