Howard Walter Florey, Baron Florey (September 24, 1898 - February 21, 1968) was a pharmacologist who shared the Nobel Prize for Physiology or Medicine in 1945 with Ernst Chain and Sir Alexander Fleming for his role in the extraction of penicillin.

Born in Adelaide, South Australia, Florey was a brilliant student (and junior sportsman) who studied medicine at the University of Adelaide from 1917 to 1921. At the university he met Ethel Reed , another medical student who was to become both his wife and his research colleague. A Rhodes Scholar, he continued his studies at Magdalen College, Oxford University.

After periods in the United States and at the University of Cambridge, he returned to Oxford, becoming a Fellow of Lincoln College and leading a team of researchers. In 1938, working with Ernst Boris Chain and Norman Heatley, he read Alexander Fleming's paper discussing the antibacterial effects of Penicillium notatum mould. His research team investigated the large-scale production of the mould and efficient extraction of the active ingredient, succeeding to the point where, by 1945, penicillin production was an industrial process for the Allies in World War II.

For his work, Florey was elevated to the peerage as Baron Florey, of Adelaide and Marston. This was a higher honour than the knighthood awarded to penicillin's discoverer, Sir Alexander Fleming, and recognised the monumental work Florey did in making penicillin available in sufficient quantities to save millions of lives in the war, despite the doubts of Fleming that this was feasible.

Florey was elected president of the Royal Society in 1959. After the death of Ethel, he married his long-time colleague and research assistant Dr. Margaret Jennings in 1967. He died of a heart attack in 1968.

Florey is regarded by the Australian scientific and medical community as probably its greatest scientist. Robert Menzies, Australia's longest-serving Prime Minister, said that 'in terms of world well-being, Florey was the most important man ever born in Australia'.

Florey's portrait appeared on the Australian $50 note for many years, and a suburb in the national capital Canberra is named after him.