Otto Loewi, German-American pharmacologist and psychobiologist, Nobel Prize laureate (died 1961)

Otto Loewi was a German-born pharmacologist and psychobiologist who discovered the role of acetylcholine as an endogenous neurotransmitter. For this discovery, he was awarded the Nobel Prize in Physiology or Medicine in 1936, which he shared with Sir Henry Dale, who was a lifelong friend that helped to inspire the neurotransmitter experiment. Loewi met Dale in 1902 when spending some months in Ernest Starling's laboratory at University College, London.

The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, according to Alfred Nobel's 1895 will, are awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". Nobel Prizes are awarded in the fields of Physics, Medicine or Physiology, Chemistry, Literature, and Peace.