Katharine O'Connor - McDermott Will & Emery


Katharine (Kate) O’Connor focuses her practice on complex antitrust litigation, antitrust investigations brought by the US antitrust regulators and state attorneys general, and counseling clients on antitrust compliance questions. Kate also regularly represents clients before the antitrust regulators related to mergers and acquisitions. Kate has experience representing clients in a wide array of industries, including healthcare, manufacturing, food and finance.

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  • Obtained highly favorable settlement on behalf of large physician practice organization in multiple disputes arising out of payor agreements
  • Obtained summary judgment defeating claims of monopolization, tying and exclusive dealing brought by an ambulatory surgery center against Southern Illinois Healthcare, a health system headquartered in Carbondale, Illinois
  • Counseled several healthcare providers and other healthcare industry participants on antitrust issues arising out of affiliations, joint ventures, competitor collaborations, and mergers and acquisitions across the country, as well as questions surrounding provider and payor contracting

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  • Crain’s Chicago Business, Women in Law, 2024
  • Chambers USA, Up & Coming, Antitrust, 2022-2023
  • The Legal 500 US, Next Generation Partner, Antitrust: Civil Litigation, 2020-2023
  • Global Competition Review, Recommended Lawyer, 2022
  • Benchmark Litigation, 40 & Under Hot List, 2019-2020, Future Star 2021-2022
  • Super Lawyers, Rising Star in Illinois: Antitrust Litigation, 2018-2019


  • American Health Lawyers Association


University of Illinois College of Law, JD, summa cum laude, Order of the Coif, 2010
University of Chicago, BA, with honors, 2001


US Court of Appeals for the Seventh Circuit
US District Court for the Central District of Illinois
US District Court for the Northern District of Illinois
US District Court for the Southern District of Illinois
US District Court for the Western District of Michigan
US District Court for the Eastern District of Wisconsin
US District Court for the Southern District of Indiana