Runciman was born in St John's Wood, North London, England, and grew up there. His father, Garry Runciman, Viscount Runciman, was a political sociologist and academic and his mother, Ruth Runciman, is former chair of the UK Mental Health Commission, a founder of the Prison Reform Trust and former chair of the National Aids Trust. His father, mother, and paternal grandfather and great-grandfather, all attended Cambridge.^[2] He was educated at Eton College, an all-boys public school in Berkshire, where he won the Newcastle Scholarship. He went on to study at Trinity College, Cambridge.^[3]

Runciman is the great-nephew of the historian Sir Steven Runciman. He inherited his family's viscountcy on the death of his father in 2020.^[4] From 1997 to 2021 he was married to the food writer Bee Wilson with whom he has three children.^[2][5] Since 2021 he has been married to psychotherapist Helen Runciman (née Lyon-Dalberg-Acton), daughter of Edward Acton.

Runciman began writing for the London Review of Books in 1996 and has written dozens of book reviews and articles on contemporary politics since, for the LRB and a number of other publications.^[6]

Runciman has published eight books. An adaptation of his PhD thesis was published in 1997 as Pluralism and the Personality of the State. The Politics of Good Intentions: History, Fear and Hypocrisy in the New World Order (2006) evaluates contemporary and historical crisis in international politics after 9/11 while Political Hypocrisy (2008) explores the political uses of hypocrisy from a historical perspective.^[7] The Confidence Trap: A History of Democracy in Crisis from World War I to the Present (2013) lays out his theory of the threat of democratic overconfidence.^[8] Profile Books published his books Politics: Ideas in Profile and How Democracy Ends in 2014 and 2018, respectively. In 2021 he published Confronting Leviathan: A History of Ideas, looking at thinkers and ideas in modern politics.

In October 2014, he was appointed head of the Department of Politics and International Studies at the University of Cambridge. Runciman gave his inaugural lecture on 24 February 2015 on Political Theory and Real Politics in the Age of the Internet.^[9] He was preceded in this position by Andrew Gamble and Geoffrey Hawthorn.

Runciman's book Politics: Ideas in Profile explores what politics is, why do we need it and where is it heading.

From 2016 to 2022, Runciman hosted a podcast called Talking Politics with professor Helen Thompson. The podcast convened a panel of academics from the University of Cambridge and elsewhere to speak about current affairs and politics. It ended in March 2022 after over 300 episodes and 26 million downloads.^[10] Runciman also hosted a spin-off podcast named Talking Politics: History of Ideas. This podcast focused on key thinkers and ideologies from throughout history.

On 27 April 2023, Runciman launched "Past Present Future: a Podcast of Ideas".

In July 2018, Runciman was elected Fellow of the British Academy (FBA).^[11]

In July 2021, he was elected Fellow of the Royal Society of Literature (FRSL).^[12]

After a negative book review in The Guardian of Antifragility by Nassim Nicholas Taleb, Taleb referred to Runciman as the "second most stupid reviewer" of his works, arguing that Runciman had missed the concept of convexity, the theme of his book. "There are 607 references to convexity", Taleb wrote.^[13][14]

Published by Profile Books in 2018, How Democracy Ends takes a look at the political landscape of the West, showing how to spot the signs that democracy may be under threat. Set out in four major sections:

1. Looking at the role of Coups in ending democracy, looking at both modern and ancient Greece in the process.
2. How major world-shattering catastrophes could kill off democracy, be that nuclear war or the climate crisis.
3. He takes a look at our rapidly changing society, specifically technologically and how the advent of artificial intelligence could soon be a problem.
4. Lastly he takes a look into the future, whether democracy will actually end and if it does, could it be replaced by something better?

Reviews of the book have been generally positively. Getting a 3.7 out of 5 stars on Goodreads^[15] and 4.2 out of 5 stars on Amazon.^[16] Andrew Rawnsley in The Guardian wrote that the book left him "feeling more positive than I thought I would be" ^[17]

• Runciman, David (1997). Pluralism and the Personality of the State. Cambridge University Press. ISBN 9780521551915.
• Runciman, David (2000). "Is the State a Corporation?". Government and Opposition. 35 (1): 90–104. doi:10.1111/1477-7053.00014. S2CID 143599471.
• Maitland, Frederic William (2003). David Runciman; Magnus Ryan (eds.). Maitland: State, Trust and Corporation; Cambridge Texts in the History of Political Thought. Cambridge University Press. ISBN 9780521526302.
• Runciman, David (2009). The Politics of Good Intentions: History, Fear and Hypocrisy in the New World Order. Princeton University Press. ISBN 9781400827121.
• Runciman, David (2010). Political Hypocrisy: The Mask of Power, from Hobbes to Orwell and Beyond. Princeton University Press. ISBN 9780691148151.
• Brito Vieira, Monica; Runciman, David (2013). Representation. John Wiley & Sons. ISBN 9780745658292.
• Runciman, David (2014). Politics: Ideas in Profile. Profile Books. ISBN 9781782831358.
• Runciman, David (2015). The Confidence Trap: A History of Democracy in Crisis from World War I to the Present. Princeton University Press. ISBN 9781400866076.
• Runciman, David (2018). How Democracy Ends. Profile Books. ISBN 9781541616783.
• Runciman, David (2019). Where Power Stops. Profile Books. ISBN 9781788163330.
• Runciman, David (2020). "Don't be a Kerensky!". London Review of Books. Vol. 42, no. 23. pp. 13–16, 18.
• Runciman, David (2021). Confronting Leviathan : a history of ideas. London. ISBN 978-1-78816-782-6. OCLC 1228314920.{{cite book}}: CS1 maint: location missing publisher (link)
• Runciman, David (2023). The Handover: How We Gave Control of Our Lives to Corporations, States and AIs. Profile Books. ISBN 1788163672.

• University of Cambridge profile page
• Works by or about David Runciman at Internet Archive
• Past Present Future podcast hosted by Runciman
• David Runciman at IMDb