Antitrust

Simpson Thacher offers a premier Antitrust and Trade Regulation Practice providing unparalleled advice on clients’ global competition needs. The Firm advises on complex, bet‑the‑company matters across major industries, with a team including former FTC and DOJ officials. Plaintiffs and defendants turn to us for high‑profile antitrust litigation, where our successes span trials, dismissals and appeals shaping antitrust law. Clients turn to us for our record in achieving regulatory clearance for the largest and most complicated M&As in history. The Firm has recently achieved landmark victories in multiple high-profile litigated merger cases versus the DOJ and FTC, including UnitedHealth Group/Change Healthcare; Tempur Sealy/Mattress Firm; and HCA/Louisiana Childrens Medical Center. We also advise on Second Request investigations, maintaining real‑time engagement with agencies on highly strategic matters. The Firm won “Merger Control Matter of the Year – Americas” at the 2026 Global Competition Review Awards for representing Amedisys in defeating the DOJ’s challenge to its UnitedHealth merger, and “Litigation of the Year – Cartel Defense” at the 2025 Global Competition Review Awards for securing dismissal affirmance for JPMorgan in ICE LIBOR litigation. The Firm was recognized as a 2026 "Global Elite" Firm by Global Competition Review in its annual GCR 100 report, and is consistently recognized as a leading antitrust practice by The Legal 500 and Benchmark Litigation.