Mark Fleming is co-chair of WilmerHale’s Appellate and Supreme Court Litigation Practice. He is an accomplished and well-regarded litigator who has appeared in more than 300 appellate cases and personally presented oral argument in 77 of them, including eight oral arguments before the Supreme Court of the United States. He has also argued before the Supreme Judicial Court of Massachusetts, the Massachusetts Appeals Court, and the First, Second, Third, Eighth, Ninth, Tenth, Eleventh, Federal, and District of Columbia Circuits.

A former US Supreme Court clerk, Mr. Fleming has filed briefs in more than 50 US Supreme Court cases on topics such as patent law, immigration, criminal law and constitutional law. Mr. Fleming argues frequently in the Federal Circuit in patent cases involving various technologies and legal issues. In November 2019, he argued three complex Federal Circuit appeals for different clients in four days. In June 2022, he won vacatur of the largest patent infringement judgment in history (over $2.7 billion), which caused Litigation Daily to recognize him as “Litigator of the Week.” In April 2023, he received that honor again as part of the WilmerHale team that convinced the Federal Circuit to vacate a patent infringement judgment of over $500 million. And within a single week in June 2025, the Federal Circuit issued three favorable decisions in appeals Mr. Fleming argued, again overturning patent infringement judgments totaling over $500 million—a victory that earned him his third recognition as “Litigator of the Week.”