Hans Karl August Simon Euler-Chelpin, since 28 July 1884 von Euler-Chelpin, 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). Euler-Chelpin was distantly related to Leonhard Euler. He married chemist Astrid Cleve, the daughter of the Uppsala chemist Per Teodor Cleve. In 1970, their son Ulf von Euler, was awarded the Nobel Prize in Physiology or Medicine.

Sir Arthur Harden, FRS was a British biochemist. He shared the Nobel Prize in Chemistry in 1929 with Hans Karl August Simon von Euler-Chelpin for their investigations into the fermentation of sugar and fermentative enzymes. He was a founding member of the Biochemical Society and editor of its journal for 25 years.