William Regner is a corporate partner, Co-Head of the firm’s Mergers & Acquisitions Group, and a member of the Technology, Media & Telecommunications, Financial Institutions, and Corporate Governance Groups. He focuses on public company transactions and corporate governance matters and advises boards, special committees and senior management on governance issues, including activist challenges and risk management. He has experience across many industries, but is particularly active in the TMT and asset management sectors. He also regularly represents investment banking firms in their roles as financial advisors in major transactions.

Mr. Regner is ranked as a leading M&A lawyer by Chambers USA (2013-2015), where sources say he is “super knowledgeable, realistic, and very pragmatic,” and he “commands a room but is also a very good listener”. He is recommended by The Legal 500 US (2012-2015) for his delivery of “high-value and to the point advice.” He is also recognized by IFLR1000 (2014) as a leading M&A lawyer.

Mr. Regner is a frequent author and speaker on legal developments affecting mergers and acquisitions. He is a co-author of Takeovers: A Strategic Guide to Mergers & Acquisitions (Wolters Kluwer Law & Business 2013) and is a contributor to Corporate Governance: Law and Practice (Matthew Bender 2013). His published articles include “Special Committees and M&A: A Half-Year Report,” The M&A Lawyer (September, 2022); “US And UK Share Purchase Agreements: Comparing Approaches,” Practical Law (January, 2015) and “How Sell-Side Advisors Can Reduce Litigation Risk in Light of Delaware’s Rural/Metro Decision,” Journal of Investment Compliance, Volume 15 Issue 2 (August, 2014). He is also a contributing author of The Private Equity Primer: The Best of the Debevoise & Plimpton Private Equity Report and the Debevoise & Plimpton Private Equity Report. Mr. Regner co-chairs the annual ALI-CLE course on corporate mergers and acquisitions.

Mr. Regner joined Debevoise as an associate in 1994 and became a partner in 2002. Mr. Regner received his A.B. from Colgate University in 1988 and his J.D. summa cum laude from the Benjamin N. Cardozo School of Law in 1994, where he was Articles Editor of the Cardozo Law Review.


  • Yeshiva University, Benjamin N. Cardozo School of Law, 1994, J.D.
  • Colgate University, 1988, A.B.

Bar Admissions

  • New York