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Mathew Rosengart is a former federal prosecutor, previously serving as a Supervisory Assistant United States Attorney and Justice Department Trial Attorney, where he investigated and prosecuted cases ranging from violent crimes to public corruption, including cases of national and international significance. 

A Governor of the Beverly Hills Bar Association and former law clerk to Justice David Souter on the New Hampshire Supreme Court, Mathew has been recognized as one of Top 100 lawyers in the State by the Daily Journal; a Sports & Entertainment Law Trailblazer by The National Law Journal; and as a Leader of Influence and Top Litigator & Trial Attorney by the Los Angeles Business Journal, which honors “masters of their craft” who “go to the proverbial mat to fight for their clients” and are “the lawyers you want in your corner.” The issue recognized Mathew as “one of the most influential litigators and trial attorneys in Los Angeles,” and a “go to litigator for Hollywood’s elite and Corporate America” who is “one of the nation’s preeminent litigators.”

Described by the New York Times as a “prominent” and “high-powered lawyer,” Mathew has also been lauded as a “legal powerhouse,” a “powerful litigator,” a “legal warrior” who is “principled,” and a “heavyweight lawyer” by Yahoo News, Newsweek, The View, Good Morning America, and The Guardian. Mathew was also recognized by NPR as a lawyer with “a lot of star power,” by Los Angeles Magazine as a “heavy hitter” with “a long history of getting results for his big name clients,” and by The Wall Street Journal, The Hollywood Reporter, and NBC’s Today as a “high profile litigator,” a “Hollywood Power Lawyer,” and a “celebrity power attorney.”

Additionally, Mathew was recently described by his client Sean Penn in a New York Times article as a “tough as nails streetfighter with a big brain and bigger principles” and by his former Justice Department supervisor and now United States District Judge Robert J. Conrad as “one of the sharpest lawyers I’ve ever met at the Department of Justice,” whose “judgment is impeccable.”

Among many other cases, Mathew recently won a defamation lawsuit for Sean Penn, a $6 million “cutting rights” case for Academy Award winner Kenneth Lonergan over his film “Margaret” starring Matt Damon, a multi-year $15 million arbitration for his client Credit Suisse against billionaire Ronald Lauer and 11 other claimants, and a $14 million trial verdict in a New York trial (on a counterclaim) after extensive bi-coastal litigation for his hedge fund client Sandton Capital against a film production company. Mathew also recently served as lead counsel for Fortune 20 company Verizon in one of the largest False Claims Act cases in the country, involving more than $500 million in claims. 

Mathew has recently twice been recognized in The American Lawyer’s “Litigator of the Week” column, for going from “defense-to-offense” for NBA superstar Jimmy Butler in a case involving Mathew’s innovative use of the California Talent Agency Act and after obtaining the suspension of Britney Spears’s father as conservator of her Estate. In addition to complex commercial litigation, Mathew has perennially been recognized as one of the nation’s leading entertainment litigators by both The Hollywood Reporter (in its 2014, 2015, 2016, 2017, and 2021 “Power Lawyer Report” issues listing the industry’s Top-100 most influential attorneys) and Variety (for eight consecutive years between 2014-2021 in its prestigious “Legal Impact Report,” spotlighting the world's leading attorneys in the entertainment industry).


  • Litigation
  • Media and entertainment litigation
  • White collar criminal defense



  • Law Clerk to Justice David H. Souter, Supreme Court of New Hampshire
  • Trial Attorney, Civil and Criminal Divisions of the United States Department of Justice 
  • Supervisory Assistant United States Attorney, United States Department of Justice 
  • Senior Associate Independent Counsel/Supervisory Assistant United States Attorney, Office of Independent Counsel 
  • Trial Attorney, United States Department of Justice, Criminal Division Campaign Finance Task Force


  • Listed, National Law Journal, "Sports, Gaming & Entertainment Law Trailblazer," 2021
  • Listed, Daily Journal, Top 100 Lawyers (listing the Top 100 lawyers in the State)
  • Listed, Los Angeles Business Journal, “Leaders of Influence: Litigators & Trial Attorneys,” 2021 (Recognizing Los Angeles’s Top Litigators and “Masters Of Their Craft”)
  • Listed, Variety, "Legal Impact Report," 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021
  • Listed, The Hollywood Reporter, "Power Lawyers: Top 100 Most Influential Entertainment Lawyers in America," 2014, 2015, 20162017, 2021
  • Featured: The American Lawyer, “Litigator of the Week” column, May and October, 2021
  • Named one of California's Top 100 Trial Lawyers, The National Trial Lawyers
  • Featured, Los Angeles Confidential Magazine, "Power Player"
  • Special Achievement Award for Meritorious Acts of Service, United States Department of Justice
  • Federal Bar Association’s Younger Lawyer Award – Awarded by Panel of Federal Judges to the Top 5 government litigators under age 36
  • Special Act Awards for Outstanding Performance, United States Department of Justice
  • Commendation, federal prosecution and conviction of defendant in United States v. Sheffield, United States Department of Justice, Bureau of Alcohol Tobacco & Firearms, Internal Affairs
  • Commendation, federal prosecution and conviction of defendant in United States v. Brisbane, United States Department of Justice
  • Board of Governors, Beverly Hills Bar Association, 2020 
  • Adjunct Professor of Law, "Criminal Procedure: Grand Jury Law & Practice," Fordham Law School, 2004-2006 
  • Adjunct Professor of Law, "White Collar Crime," Pepperdine University School of Law, 2007 
  • Faculty, United States Attorney General's National Advocacy Center, lecturing in Trial Practice, 2000
  • Dean's Advisory Council, Tulane University
  • Member, Association of Business Trial Lawyers Los Angeles


  • 法務博士, cum laude, Boston College Law School
  • 学士号, Tulane University
  • カリフォルニア州
  • 米国 ニューヨーク州
  • U.S. District Court for the Southern District of New York
  • U.S. District Court for the Eastern District of New York
  • U.S. District Court for the Central District of California