Mark Weiss is a partner in the Firm's North America Antitrust & Competition Practice Group and the North American Chair of the Practice’s Litigation Task Force. He is a seasoned litigator with deep expertise in antitrust, class action, and federal multi-district litigation and represents clients in high-stakes disputes across a range of industries, with a focus on complex commercial and competition-related claims. Mark defends clients in nationwide class actions and seamlessly navigates the procedural and strategic challenges of MDLs in federal court. Mark’s is also a highly regarded criminal antitrust attorney with significant experience representing clients in complex cartel investigations and enforcement actions. Mark has a strong track record advising corporations and executives in high-stakes matters involving the U.S. Department of Justice’s Antitrust Division, particularly in cases involving leniency and cooperation strategies. He has a deep understanding of the leniency program and is a trusted advisor in navigating cross-border investigations. Mark also has extensive experience as a leading antitrust merger attorney and has led numerous clients through complex regulatory reviews and merger clearance processes. He advises on all aspects of pre-merger strategy, including Hart-Scott-Rodino (HSR) filings, competitive risk assessments, and engagement with the Federal Trade Commission and Department of Justice. Mark advises clients on a wide range of antitrust compliance issues, helping companies design and implement effective compliance programs tailored to their business operations and risk profiles. Mark is an expert in handling matters consistent with recent antitrust trends including artificial intelligence, algorithmic pricing, information-sharing, and both vertical and horizontal practices. He regularly conducts internal audits, risk assessments, and training for legal and business teams, and provides strategic guidance on interactions with competitors, pricing practices, and distribution arrangements.