John Neill Greenwood was born at St Helens, in England, on 12 December 1894. He was educated at the University of Manchester, receiving a DSc in 1922.

He was Professor of Metallurgy and Applied Science at the University of Melbourne from 1924 to 1945, and Research Professor at the same University from 1946 to 1964. He was appointed Emeritus Professor in 1965.

Greenwood's obituary in The Australasian Institute of Mining and Metallurgy acknowledges his commitment to education and research:

In the fields of physical metallurgy and metal physics Greenwood built up a teaching and research establishment in the University of Melbourne with an outstanding international reputation, commencing from the grass roots.

He died in Mornington, Victoria, on 30 August 1981.