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John O'Sullivan is a leading trial lawyer handling high-stakes business disputes for top global clients. Chambers and Partners describes him as a "strong presence" in the courtroom who is "brilliant at breaking down complex problems so they are easy to understand." Clients praise John’s "brilliantly concise courtroom and written advocacy, and high-level strategic and tactical insight" and describe him as “very thorough, super smart and easy to work with.” He has more than 25 years of experience litigating a wide range of complex commercial matters.

Best Lawyers in America recently named John its “Lawyer of the Year” for Litigation: Banking and Finance in New York City, 2022.  John has also been named “Litigator of the Week” by The AmLaw Litigation Daily, for his work securing an injunction against the State of Florida barring enforcement of a Florida statute which prohibited his client Norwegian Cruise Lines from requiring vaccine documentation. John is a Fellow of the International Academy of Trial Lawyers, recognized as the most prestigious organization of trial lawyers in the world, and is included in all of the major guides identifying top lawyers. John is dedicated to pro bono: the Legal Aid Society, Voices for Children, and numerous other legal services organizations have recognized him for his efforts on behalf of pro bono clients.

Whether it's breach of contract and tortious interference claims or patent, trademark, and copyright litigation, John's vast experience helps him help clients. John also handles trade secret and Lanham Act actions; unfair competition, price fixing, and monopoly claims; and real estate, banking, and construction litigation. He is also actively involved in securities and corporate governance disputes and professional negligence and malpractice matters.

In addition to his law practice, John teaches Advanced Civil Procedure at The University of Miami School of Law and also serves as a Senior Fellow at the UM Center for Ethics and Public Service.

Prior to practicing, John served as a law clerk for the Honorable William H. Timbers on the United States Court of Appeals for the Second Circuit.

  • Won dismissal with prejudice of claims brought by Florida cities against banks seeking billions in damages for lost tax revenue in litigation ultimately heard by the U.S. Supreme Court.
  • Prevailed in multi-jurisdiction litigation over ownership of real estate and financial assets valued at nearly US$1bn.
  • Represented a minority shareholder with an interest in the subsidiary of a publicly-traded, international cannabis company valued at $4b in a suit seeking dissolution of the entity for shareholder oppression.  Prevailed after an 8-day trial proceeding in New York, resulting in a buy-out of the client’s interest at a materially higher valuation than previously offered.
  • Obtained preliminary injunction for life sciences client preserving more than US$1bn in sales.
  • Won at trial for consumer products company in dispute over ownership of formulas for client's best-selling products.
  • Obtained dismissal with prejudice of securities claims seeking US$190m against a ratings agency alleging fraudulently inflated RMBS ratings.
  • Obtained one of the largest sanctions awards on record in Florida based on showing that principal of opposing party gave false deposition testimony.
  • Litigation counsel for clients in connection with many of the most prominent real estate assets in South Florida.
  • Represented an international financial consulting firm in extensive litigation related to the third-largest Ponzi scheme in American history.  After proceedings in federal bankruptcy court, federal district court, and before the Eighth Circuit Court of Appeals, won dismissal with prejudice of claims seeking hundreds of millions of dollars in damages.
  • Obtained a dismissal with prejudice for a major Japanese bank in a US$200m lender liability suit arising from Florida real estate investments.
  • Obtained a nationwide permanent injunction on behalf of a major broadcasting network in a copyright infringement suit against a satellite TV provider.
  • The George Washington University Law School
    (J.D., with honors, 1988)
    Trustee Scholar
    Member, George Washington Law Review
  • University of Massachusetts Amherst
    (B.A., cum laude, 1985)
  • University of Sussex
    (Economics & International Relations Program, 1984)
  • The State Bar of Florida
  • The State Bar of New York
  • United States District Court:
    • Middle District of Florida
    • Northern District of Florida
    • Southern District of Florida
    • Southern District of New York
    • District of Minnesota
  • United States Court of Appeals:
    • Second Circuit
    • Seventh Circuit
    • Eighth Circuit
    • Eleventh Circuit
    • Federal Circuit
  • United States Bankruptcy Court:
    • Middle District of Florida
    • Northern District of Florida
    • Southern District of Florida
    • District of South Dakota
  • United States Supreme Court
  • Hogan Lovells LLP:
    • Partner, 2005-2021
  • Akerman LLP:
    • Partner, 1998-2005
  • Paul, Weiss, Rifkind, Wharton & Garrison LLP:
    • Associate, 1989-1998
  • Law Clerk for the Honorable William H. Timbers:
    • United States Court of Appeals for the Second Circuit
  • Best Lawyers in America, Litigation: Banking and Finance - “Lawyer of the Year” in New York City, 2022
  • Best Lawyers in America, Commercial Litigation, 2010-2022
  • Best Lawyers in America, Litigation: Banking and Finance, 2010-2022
  • Best Lawyers in America, Litigation: Real Estate, 2010-2022
  • Named "Litigator of the Week” by The AmLaw Litigation Daily, 2021
  • Chambers USA, Litigation: General Commercial (Florida), 2009-2013, 2017-2021
  • Florida Super Lawyers, Business Litigation, 2008-2013, 2017-2020
  • Top Rated Lawyers, Commercial Bankruptcy Creditor-Debtor Rights, 2012
  • Super Lawyers: Corporate Counsel, Business Litigation, 2009-2010
  • The Legal Aid Society, Outstanding Volunteer Lawyer Award
  • Voices for Children, Inc., Most Valuable Protector (MVP) Award, 2008
  • 11th Judicial Circuit, Community Advocate of the Year, 2008
  • International Academy of Trial Lawyers, Fellow
  • University of Miami Center for Ethics and Public Service, Senior Fellow
  • University of Miami School of Law, Adjunct Professor