U. Seth Ottensoser


(212) 653-9715

Seth Ottensoser is a Partner at Keller Lenkner LLC. He represents investors—including pension funds, labor unions, hedge funds, and individual shareholders—in merger-and-acquisition litigation, securities class actions, and corporate litigation. Seth’s track record includes successful class actions that have generated more than $3.3 billion in resolutions. Those matters include:

  • In re Cablevision Systems Corp. Shareholders Litigation (N.Y. Sup. Ct.) (successfully blocked a going-private transaction by a controlling shareholder, leading to payment of a dividend worth approximately $2.5 billion).

  • In re Marsh & McLennan Cos., Inc. Securities Litigation (S.D.N.Y.) ($400 million recovery)

  • In re Freeport-McMoRan Copper & Gold, Inc. Derivative Litigation (Del. Ch.) ($153.5 million recovery, representing the second largest derivative settlement in Delaware)

  • In re Aetna, Inc. Securities Litigation (E.D. Pa.) ($82.5 million recovery)

  • In re Plains Resources, Inc. Shareholders Litigation (Del. Ch.) ($67 million in additional merger consideration for the shareholders of Plains Resources)

  • In re Triton Energy Ltd. Securities Litigation (E.D. Tex.) ($49.5 million recovery)

  • In re Ascent Entertainment Derivative Litigation (Del. Ch.) ($40 million derivative settlement relating to the sale of the Denver Nuggets and the Colorado Avalanche)

  • City of Austin Police & Retirement Fund v. Kinross Gold Corp. (S.D.N.Y.) ($33 million settlement)

  • In re Waste Management Derivative Litigation (Del. Ch.) ($25 million recovery)

  • In re UnitedGlobalCom Shareholders Litigation (Del. Ch.) ($25 million recovery in a going-private transaction)

For his work in securities litigation, Seth has been repeatedly named a leading lawyer by Super Lawyers Magazine (2010, 2013-2018) and Super Lawyers Business Editions (2011, 2013-2015). In addition, he is recommended by The Legal 500 (2011, 2012, 2016).

Seth lectures on civil procedure, federal practice, class actions, securities regulation, corporate finance, litigation finance, and corporate governance, and has also been published extensively on those matters. He is a frequent guest lecturer at Harvard Law School and has served as a member of the Special Committee on Mergers, Acquisitions and Corporate Control Contests of the New York City Bar Association.

Seth received his J.D. from the University of Southern California School of Law after graduating with high honors from Queens College of the City University of New York, where he was elected to Phi Beta Kappa.