Hans Karl August Simon von Euler-Chelpin (15 February 1873 – 6 November 1964) was a German -born Swedish biochemist. He won the Nobel Prize in Chemistry in 1929 with Arthur Harden for their investigations on the fermentation of sugar and enzymes. He was a professor of general and organic chemistry at Stockholm University (1906–1941) and the director of its Institute for organic-chemical research (1938–1948). Von Euler-Chelpin married Astrid Cleve, the daughter of the Uppsala chemist Per Teodor Cleve and was the great-great-great grandson of Leonhard Euler. In 1970, his son Ulf von Euler, was awarded the Nobel Prize in Physiology or Medicine.