John Zachary Young FRS[1] (18 March 1907 – 4 July 1997), generally known as "JZ" or "JZY", was an English zoologist and neurophysiologist, described as "one of the most influential biologists of the 20th century".

On Oct. 12, 1942, Young spoke at the Socratic Club in Oxford on the topic "Purpose and Design in Nature" as part of the series of talks and debates led by C. S. Lewis.

Working with Peter Medawar, Young found a way to rejoin small peripheral nerves using a "glue" of plasma.

After WWII, Young's research interests turned to investigating the central nervous system and the functions of the brain.

He discussed and corresponded with the mathematician Alan Turing on brain cells, memory, pattern recognition, and embryology, from 1949.

In his series of eight radio broadcasts, titled Doubt and Certainty in Science, he introduced the BBC audience to the themes of his research, exploring the function of the brain and the then-current scientific methods used to increase understanding of it.

For most of his retirement, he continued to work both at the Stazione Zoologica in Naples and at a laboratory in the Psychology Department of Oxford University, and to publish scientific papers.

[1] Young married twice, to Phyllis Heaney (a painter) with whom he had two children, Simon Zachary and Cordelia, and in 1987, following her death, to Raymonde Parsons (also an artist) with whom he had one child, Kate Frances.