John Simpson was born in Cheltenham, where his father was employed at GCHQ, and attended Dean Close School. He gained a BA in English Literature at the University of York in 1975 and a MA in Medieval Studies at the University of Reading in 1976.
He is married with two daughters and two granddaughters, and lives in Cheltenham.
John Simpson joined the editorial staff of the OED in 1976 to work on the Supplement to the OED. He was Co-Editor of the Second Edition of the OED, published in 1989, and in 1993 was appointed Chief Editor, a position he held until his retirement in October 2013. As Chief Editor, he led the first comprehensive revision of the OED and oversaw the introduction of its online version.
John Simpson is a member of the English Faculty at the University of Oxford, an Emeritus Fellow of Kellogg College, Oxford, and a member of the Philological Society, where the idea of the Dictionary was first proposed in the 1850s. He is a founder member of the European Federation of National Institutions for Language and has been a member of its Executive Committee since 2003. He has acted as an adviser to a number of other national dictionaries, including the Opera del Vocabolario Italiano and the Australian National Dictionary.
He has been awarded two D.Litt degrees, the first in 1999 by the Australian National University for his "distinguished creative achievement as a scholar in lexicography", and the second in 2015 by the University of Leicester for his work on the OED. He was appointed Officer of the Order of the British Empire (OBE) in the 2014 Birthday Honours for services to literature.
John Simpson edited the Concise Oxford Dictionary of Proverbs (1982) and co-edited the Oxford Dictionary of Modern Slang (1992). He wrote introductions to Robert Cawdrey's Table Alphabeticall (1604), B.E.'s Dictionary of the Canting Crew (1699), Francis Grose's Popular Superstitions (1787), and James Redding Ware's Victorian Dictionary of Slang and Phrase (1909), published by the Bodleian Library. He co-edits James Joyce Online Notes, a forum for the publication of documentary evidence about the people, words and cultural references in James Joyce's fiction.