Ulf Svante von Euler (7 February 1905 – 9 March 1983) was a Swedish physiologist and pharmacologist. He won a Nobel Prize in Physiology or Medicine in 1970 for his work on neurotransmitters.

Ulf von Euler discovered norepinephrine (also called noradrenaline, a crucial carrier of impulses in the sympathetic nervous system) and prostaglandins (the hormones which stimulate muscle contraction and help regulate the cardiovascular and nervous systems).

He studied under Nobel laureates Henry Dale, Archibald V. Hill, and Corneille Heymans, and received the Nobel Prize for Medicine or Physiology in 1970, sharing the honors with the American Julius Axelrod and German-born Englishman Bernard Katz. His father, Hans von Euler-Chelpin, won the Nobel Prize in Chemistry in 1929, and his mother, Astrid Cleve, was a botany and geology professor.

His godfather was Nobel laureate Svante Arrhenius, his maternal grandfather was Per Theodor Cleve, who discovered the elements holmium (Ho) and thulium (Tm), and the famed 18th-century mathematician Leonhard Euler was among his family's ancestors.

His short stay as a postdoctoral student in Dale's laboratory was very fruitful: in 1931 he discovered with John H. Gaddum an important autopharmacological principle, substance P. After returning to Stockholm, von Euler pursued further this line of research, and successively discovered four other important endogenous active substances, prostaglandin, vesiglandin (1935), piperidine (1942) and noradrenaline (1946).

In 1939 von Euler was appointed Full Professor of Physiology at the Karolinska Institute, where he remained until 1971. His early collaboration with Liljestrand had led to an important discovery, which was named the Euler-Liljestrand mechanism (a physiological arterial shunt in response to the decrease in local oxygenation of the lungs).

From 1946 on, however, when noradrenaline (abbreviated NA or NAd) was discovered, von Euler devoted most of his research work to this area