Nelson was educated at Keswick School, Cumbria and at Newnham College, Cambridge where she earned her BA degree in 1964 and her PhD degree in 1967. She was appointed a Lecturer at King's College, London in 1970, promoted Reader in 1987, Professor in 1993 and Director of the Centre for Late Antique and Medieval Studies in 1994, retiring in 2007. She was a Vice-President of the British Academy, 2000–2001, and President of the Royal Historical Society in 2000–04. She has honorary doctorates from the University of East Anglia (2004) and St Andrews University (2007).
Her research to date has been focused on early medieval Europe, including Anglo-Saxon England. She has published widely on kingship, government, political ideas, religion and ritual, and increasingly on women and gender during this period.
She has co-edited and/or written the following:
- Courts, Elites and Gendered Power in the Early Middle Ages (Aldershot, 2007)
- (with P. Wormald) ed., Lay Intellectuals in the Carolingian World (Cambridge, 2007)
- ed., Timothy Reuter, Medieval Politics and Modern Mentalities (Cambridge, 2007)
- (with P. Stafford and J. Martindale) ed., Law, Laity and Solidarities: Essays in Honour of Susan Reynolds (Manchester, 2001)
- (with P. Linehan) ed.,The Medieval World (London, 2001)
- (with F. Theuws) ed., Rituals of Power from Late Antiquity to the Early Middle Ages (Leiden, 2000)
- Rulers and Ruling Families in Earlier Medieval Europe (London, 1999)
- The Frankish World (London, 1996)
- Charles the Bald (London, 1992)
- Politics and Ritual in Early Medieval Europe (London, 1986)
Her biographical study, Charles the Bald, her annotated translation of The Annals of St-Bertin and her papers reflect her interest in Frankish kingship and in the Vikings on the Continent, while her papers on Alfred of Wessex address comparable themes in Anglo-Saxon history.
- "Birthdays", The Guardian, 28 March 2014: 43
- NELSON, Dame Janet Laughland, (Dame Jinty Nelson), Who's Who 2009, A & C Black, 2008; online edn, Oxford University Press, Dec 2008 accessed 3 Sept 2009
- BBC Four - King Alfred and the Anglo Saxons. Accessed 21 August 2013