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Kathleen (Katie) M. O'Sullivan

Profile photo for Katie O'Sullivan
Profile photo for Katie O'Sullivan
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Kathleen (Katie) M. O'Sullivan

  • Seattle
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A veteran litigator and community leader, Katie helps businesses with critical legal matters.

With more than 25 years of practice, Katie O'Sullivan represents businesses facing high-stakes litigation, including trial court cases and appeals. She regularly advises Fortune 100 and other leading companies across industries in consumer class actions, pending investigations, and other related cases. Katie also works on appeals across a broad spectrum of legal issues, including antitrust, contracts and business torts, environmental law, product labeling, privacy, and product liability.

Katie emphasizes high-quality written and oral advocacy in her litigation practice and as a leader in the firm. Katie served as the chair of the firm's Executive Committee from 2020 to 2024, during which time she led the development of the firm's strategic plan. She is also the former firmwide chair of the Commercial Litigation practice.

Katie is an active member of the legal community and has served on the Washington State Bar Association Board of Governors and chaired the Washington State Commission on Judicial Conduct. Katie currently serves on the American Law Institute Council and the Ninth Judicial Circuit Historical Society board. She is a former chair of the Board of Directors of the YMCA of Greater Seattle.

Education & Credentials

Education

  • Georgetown University Law Center, J.D., cum laude, Senior Notes Editor, Georgetown Law Journal
  • Yale University, B.A., History, cum laude

Bar and Court Admissions

  • Washington
  • Supreme Court of the United States
  • U.S. Court of Appeals for the Fourth Circuit
  • U.S. Court of Appeals for the Sixth Circuit
  • U.S. Court of Appeals for the Seventh Circuit
  • U.S. Court of Appeals for the Ninth Circuit
  • U.S. District Court for the Eastern District of Washington
  • U.S. District Court for the Western District of Washington

Related Employment

  • Miller Cassidy Larroca & Lewin, Washington, DC, Summer Associate, 1996
  • Perkins Coie, Seattle, WA, Summer Associate, 1995
  • DNA – People’s Legal Services, Window Rock, Navajo Nation, AZ, Law Clerk, 1994

Clerkships

  • Hon. Harold H. Greene, U.S. District Court for the District of Columbia
  • Hon. M. Margaret McKeown, U.S. Court of Appeals for the Ninth Circuit

Professional Recognition

  • Listed in Chambers USA as "America’s Leading Litigation Lawyer" 2018-2024

  • Named Best Lawyers "Lawyer of the Year" for Appellate Practice, 2016, 2024; for Bet-the-Company Litigation, 2025

  • Listed in Best Lawyers in America: Appellate Practice; Bet-the-Company Litigation; Commercial Litigation, 2009-2025

  • Listed in Super Lawyers Magazine, “Washington's Super Lawyers," 2007-2024

  • Co-Recipient of awards for IOLTA Supreme Court litigation (American Bar Association, Washington State Bar Association, King County Bar Association, Perkins Coie)

Impact

Professional Leadership

  • Ninth Judicial Circuit Historical Society, Board Member, 2017-present
  • Elected to governing Council of American Law Institute (2015); member of American Law Institute since 2006
  • Washington Commission on Judicial Conduct, Lawyer Member, 2007-2015; Chair, 2012-2014
  • Ninth Circuit Appellate Lawyer Representative, 2010-2013
  • Federal Bar Association for the Western District of Washington, Chair of Appellate Practice Committee, 2007 and 2008
  • Washington State Bar Association, Board of Governors, 2003-2006

Community Involvement

  • YMCA of Greater Seattle, Board Chair (former); Executive Committee member (former); Board member, 2011-present
  • Perkins Coie Campaign for United Way of King County, Chair, 2009-2012 
  • Leadership Tomorrow, Class of 2009
  • Passages Northwest, Board Member, 2000-2003
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