Books:
* The Welsh Society: 1536-1914 (1980): A seminal work that examines the social and economic development of Wales during this period.
* The Making of Modern Wales (1982): Another major work that traces the history of Wales from the Tudor period to the 20th century.
* Castles and Communities in Medieval Wales (1984): A study of the relationship between castles and the surrounding communities in medieval Wales.
* Wales: A History (1989): A comprehensive history of Wales, covering all periods from the earliest times to the present day.
* Wales: A Nation in the Making (2004): An exploration of the historical and cultural development of Wales, emphasizing the themes of identity, language, and politics.
Edited works:
* The Welsh Church from Reformation to Disestablishment (1980): A collection of essays on the history of the Church in Wales.
* The History of Wales (2003): A collection of essays by leading Welsh historians.
Articles and essays:
Williams has also written numerous articles and essays on Welsh history, published in academic journals and edited volumes. His research interests include:
* The social and economic history of Wales
* The history of Welsh politics
* The history of the Welsh language
* The history of the Welsh Church
Glyndwr Williams's work has been praised for its scholarship, clarity, and insight. He is considered one of the leading authorities on Welsh history.