Maggy Sullivan is a partner in the Litigation & Trial Department of Latham & Watkins and is a member of the firm’s Antitrust & Competition Practice. She is a former member of the firm’s Finance Committee and Strategic Client Committee. She has significant experience advising on both private and government antitrust matters, and has defended corporate clients in merger challenges, cartel investigations, complex civil actions, multi-district actions, and class actions. 

Ms. Sullivan focuses on consumer and antitrust class actions, business to business litigation, merger litigation, criminal cartel investigations, and antitrust compliance counseling. She has been involved in some of the largest and most complex antitrust matters to date. 

Ms. Sullivan’s antitrust work has covered a wide range of industries, including: 

  • Energy 
  • Consumer products 
  • Healthcare 
  • Automotive 
  • Software and technology 
  • Construction materials 
  • Specialty chemicals 
  • Textiles 
  • Medical dictation 
  • Paper 
  • Cable and satellite 

Ms. Sullivan received Global Competition Review’s 2017 award for Cartel Defense Civil Litigation of the Year for her work resolving multiple class action claims against global auto parts suppliers. In 2021 and 2022, Ms. Sullivan was recognized by Chambers USA for her expertise in antitrust work. She has also been recommended for her cartel defense practice by The Legal 500 US. Ms. Sullivan spent two years practicing in Brussels where she was listed in Chambers 2016 and 2017 as one of the leading antitrust and competition lawyers in Brussels and recognized for her private antitrust litigation expertise and her extensive experience acting before the US Department of Justice. Ms. Sullivan has also been named as a Benchmark Litigation 2018 and 2022 Future Star and is featured on the Who’s Who Legal: Future Leaders 2017 – Competition list. In 2012, Ms. Sullivan was recognized as a Rising Star in Litigation at Euromoney’s inaugural America's Women in Business Law awards.

Thought Leadership

Ms. Sullivan regularly writes on antitrust issues. A selection of her publications includes: 

  • “Supreme Court to Decide Whether Federal Courts can Consider Challenges to the Constitutionality of the FTC’s Administrative Process,” ABA Antitrust Law Section, January 2022
  • “Key Aspects of DOJ’s Gov’t Procurement Antitrust Initiative,” Law360, November 2019
  • “New DOJ Guidance Increases Benefits for Robust Antitrust Compliance Programs - What Companies Need to Know,” Client Alert, July 2019
  • “US DOJ Weighs Reform Options for Antitrust Leniency Law Set to Expire,” Client Alert, April 2019 
  • “Ninth Circuit Nixes Immediate Appeals of Denials of State Action Immunity,” Client Alert, June 2017 
  • “Class Action Defendants Likely to Benefit if House Bill Becomes Law,” Client Alert, March 2017 
  • “Your Stipulated Protective Order May Not Provide As Much Protection As You Expect,” Client Alert, October 2016 
  • “Class/Collective Actions in Europe: Overview of Applicable EU Law Principles;” chapter within the book Class Actions – A Global Guide from Practical Law, 2015 
  • “Resale Pricing Issues,” Antitrust Law and Economics of Production Distribution, ABA Antitrust Section, 2013 
  • “Three Years After Credit Suisse v. Billing: Courts Still Find The Implied Immunity Doctrine Plainly Repugnant,” Antitrust Practitioner, Vol. 7, October 2010 
  • “Breaking New Ground: Direct Settlement of EC Cartel Cases,” Global Competition Review, 2008 

Her recent speaking engagements include: 

  • “A New Era in Global Cartel Enforcement: What to Expect from a Biden Department of Justice and Implications for the Global Antitrust Enforcement Landscape, ” Latham & Watkins Webcast, March 2021
  • “‘Oh no! We got nailed’ – Compliance after the worst case scenario,” GCR Live 8th Annual Antitrust Law Leaders Forum, Miami, FL, February 2019
  • “Developments in Cartel Enforcement in Asia and Beyond,” ABA’s Antitrust in Asia Conference, Seoul, Korea, June 2018
  • Proposed Changes to the Canadian Immunity and Leniency Programs, BLG’s Competition/Antitrust Developments Conference, Toronto, Canada, September 2017
  • Managing Global Litigation, GCR Live 3rd Annual Antitrust Litigation USA, NY, June 2017
  • ABA Fall Forum Panel on Litigating State Regulation of Disruptive Technologies, Washington, D.C., November 2016 
  • Private Antitrust Litigation: Europe v. U.S. – A Comparative Discussion Providing Practical Advice for A Successful Global Defense Strategy, Latham & Watkins Seminar, Tokyo, Japan, March, 2016

Ms. Sullivan’s recent successes include defeating class certification in consumer class actions alleging unfair business practices, winning dismissal in an antitrust class action based on the plaintiffs’ insufficient conspiracy allegations, securing amnesty for a global industrial corporation in multiple jurisdictions around the world, obtaining the first ever global resolution of criminal and civil claims (including antitrust and False Claims Act claims) asserted by the US Government on favorable terms and in record time, and obtaining dismissal of monopolization claims against a natural gas and energy supplier based on the Filed Rate Doctrine and lack of antitrust standing. 

With respect to merger litigation, Ms. Sullivan has tried two of the most closely watched merger challenges in recent years: the FTC’s lawsuit challenging genomics company Illumina’s acquisition of GRAIL, and the DOJ’s lawsuit challenging aluminum manufacturer Novelis’ acquisition of Aleris (the first ever DOJ merger challenge to be resolved through arbitration).

She currently represents American Airlines in litigation against the DOJ and several states, in which the plaintiffs are seeking to unwind the Northeast Alliance, a joint venture between American and JetBlue.

Examples of multidistrict class actions in which Ms. Sullivan has played a leadership role include: 

  • In re Generics Pharmaceuticals Antitrust Litigation
  • In re Inductors Antitrust Litigation 
  • In re Auto Parts Antitrust Litigation
  • In re Aftermarket Filters Antitrust Litigation 
  • In re Baby Products Antitrust Litigation 
  • In re Pressure Sensitive Labelstock Antitrust Litigation 
  • In re Polyester Staple Antitrust Litigation 

Bar Qualification

  • District of Columbia
  • Virginia


  • JD, Northwestern University School of Law, 2000
  • BA, Bowdoin College, 1995