German-born British physiologist who investigated the functioning of nerves and muscles. His studies on the release of the neurotransmitter acetylcholine—which carries impulses from nerve fibre to muscle fibre or from one nerve ending to another—won him a share (with Julius Axelrod (Axelrod, Julius) and Ulf von Euler (Euler, Ulf von)) of the 1970 Nobel Prize for Physiology or Medicine.

After receiving a medical degree from the University of Leipzig in 1934, Katz immigrated to England, where he pursued advanced studies at University College in London, taking a Ph.D. in 1938. Upon receiving a Carnegie fellowship, he studied in Australia (1939–42) and then served in the Royal Australian Air Force during World War II. He returned to University College in 1946 and from 1952 to 1978 was professor and head of the biophysics department. Katz was knighted in 1969.

Katz wrote Electric Excitation of Nerve (1939), Nerve, Muscle and Synapse (1966), and The Release of Neural Transmitter Substances (1969). He and his associates made numerous discoveries concerning the chemistry of nerve transmission, including the role of calcium ions in promoting the release of neurotransmitter substances and the fact that quanta of these substances are being released constantly at random intervals.