Mark Ryan is a partner in Mayer Brown’s Washington DC office and the head of the firm’s Global Antitrust & Competition group. Mark has extensive experience representing clients before the Federal Trade Commission and the Antitrust Division of the Department of Justice in connection with mergers and acquisitions. Mark is also one of the nation’s leading antitrust litigators. He recently rejoined Mayer Brown after serving as the first-ever Director of Litigation for the Justice Department’s Antitrust Division. In that position, Mark was responsible for overseeing and strengthening the Division’s litigation enforcement efforts. He worked regularly with staff lawyers and economists, as well as the senior leadership of the Division, to identify transactions and conduct that violated U.S. antitrust law and to assemble investigative and litigation teams. He also participated in litigation on behalf of the United States, including acting as lead trial lawyer in the e-books price-fixing litigation in the Southern District of New York and as a member of the trial team that successfully sued a major credit card issuer in the Eastern District of New York over anti-steering rules contained in merchant agreements. These lawsuits are widely regarded as two of the most important government antitrust cases in recent years. He also led the Division’s trial teams that challenged the InBev/Grupo Modelo and US Airways/American Airlines mergers. Both mergers were resolved by settlement after the United States filed suit. At the end of his tenure at the Justice Department, Mark was the lead trial lawyer in a challenge to the proposed merger of the two largest cinema advertising companies in the country, which the parties abandoned completely shortly before trial, a result that Assistant Attorney General Bill Baer lauded as “a testament to the strength of the Antitrust Division’s case and the hard work of our talented litigation team.”

Mark went to the Department of Justice from Mayer Brown, where he held several key positions, including as a firm-wide litigation practice leader and as partner-in-charge of the Washington DC office. In over 25 years of private practice he has appeared in federal and state courts across the nation on behalf of large multinational corporations, small companies and individuals. In addition to high stakes litigation, Mark advises corporations on the potential antitrust consequences of distribution strategies, joint ventures, mergers and acquisitions. He also represents companies and individuals in cartel investigations.

Recently The Washington Post named Mark a “Best Lawyer in DC” for Antitrust in 2017. In 2011, before joining the Justice Department, Mark was one of 15 antitrust lawyers in the nation selected to the BTI Client Service All-Stars after a survey of corporate counsel aimed at identifying lawyers with a combination of legal knowledge and “a deep understanding of their client’s business objectives.” Chambers USA writes about Mark that, “business people like him-he takes the complex world of antitrust and breaks it down into bite-sized pieces.”

Mark was lead antitrust counsel for the Chicago Board of Trade in its merger with the Chicago Mercantile Exchange, a combination of two of the largest futures exchanges in the world. He has handled many other mergers of principal competitors throughout his career. He has also served as regular antitrust counsel to one of the world’s largest traders of commodities and has advised major agricultural firms on cartel and related competition matters.

In addition to antitrust, Mark has represented boards of directors in shareholder derivative actions and in disputes with former senior executives. He has represented clients in trials of government and private lawsuits arising from bank failures and the collapse of the mortgage-backed securities market and handled numerous matters on behalf of major accounting firms.

Spoken Languages

  • English
Secrets of a Successful Trial Strategy


  • Represented an antitrust plaintiff in one of only a few monopolization claims in recent years in which a federal jury awarded large treble damages and in which the award was affirmed on appeal. The case involved an action by a small firm against an entrenched monopolist and the monopolist’s efforts to block access to critical distribution channels. A judgment following a nine week trial was upheld by the US Court of Appeals for the Third Circuit sitting en banc.
  • Represented one of the nation’s largest meatpackers in the successful jury trial and appeal of a lawsuit brought by a nationwide class of beef producers.
  • Obtained a favorable jury verdict on behalf of a defendant in a Robinson-Patman Act case.
  • Represented one of the world’s largest food ingredient companies in connection with government price-fixing investigations and resulting class action litigation in which the alleged damages totaled billions of dollars.
  • Represented a marine engine manufacturer in several acquisitions reviewed by the Federal Trade Commission, all concluding without objection, and in an extended FTC investigation of the manufacturer’s rebate and discount policies that ended without any enforcement action.
  • Litigation counsel to a board of directors in a shareholder derivative action alleging that a corporate asset was sold to an affiliate in a manner that favored the corporation’s majority shareholder over minority shareholders. The successful defense was affirmed by the Maryland Court of Appeals and is now a leading Maryland case on the scope of the shareholder demand rule.
  • Defeated the Office of the Comptroller of the Currency in a several week trial arising from the collapse of a bank brought about by a fraudulent subprime lending program. On appeal, the judgment was affirmed in a decision establishing important limitations on the OCC’s ability to pursue administrative penalty actions against outside service providers; in related litigation established precedent limiting the scope of the “fraud on the market” doctrine in securities fraud class actions.
  • On the eve of a trial, based on newly developed evidenced and other pre-trial efforts, obtained the release from prison of an indigent criminal defendant who had served two years of a mandatory twenty year sentence.


Duke University School of Law, JD

Syracuse University, BA, magna cum laude


  • District of Columbia
  • Maryland


  • US Supreme Court
  • US Court of Appeals for the District of Columbia Circuit
  • US Court of Appeals for the Third Circuit
  • US Court of Appeals for the Fourth Circuit
  • US Court of Appeals for the Eighth Circuit
  • US Court of Appeals for the Ninth Circuit
  • US Court of Appeals for the Eleventh Circuit
  • Maryland Court of Special Appeals


  • American Bar Association, Antitrust Section, Vice Chair, Agriculture and Food Committee (former)