Denise Patricia Byrne Kingsmill, Baroness Kingsmill CBE is a British Labour peer. She was appointed as a life peer to the House of Lords in 2006 after a career as a lawyer specialising in trade union and employment law. She was born in New Zealand and emigrated to Wales during her childhood. She studied at Croesyceiliog School.

Lady Kingsmill headed inquiries into banking, cruise liners, equity underwriting, energy supply, and other subjects during her time as Deputy Chair of the Monopolies and Mergers Commission, a role she started in 1997 and stepped down from in 2004.

Her other roles include Non-executive directorship of British Airways, Trustee of the Cambridge University Judge Business School, Pro-chancellor of Brunel University and Trustee of The Design Museum. She was also chair of the Southwark and Lewisham NHS Trust and chair of Sadler's Wells Theatre.

Lady Kingsmill holds a degree in Economics and Anthropology from Girton College, Cambridge.
A former partner at a leading London law firm, Baroness Kingsmill has held a series of high-profile non executive director and advisory roles in the private sector, including at British Airways, Laing O’Rourke, Royal Bank of Scotland and Telewest Communications. She has also advised top international companies on their expansion in Europe and their relations with the European Union.

As well as her senior private sector roles, Baroness Kingsmill has held influential positions in the public arena, including the Deputy Chairmanship of the Competition Commission. Baroness Kingsmill is a life peer and sits in the House of Lords where she is a member of the influential Economic Affairs Committee.