Mathew S. Rosengart

Los Angeles

Mathew Rosengart commands attention in courtrooms across the country, representing A-list celebrities, tech giants and entertainment industry powerhouses in their most consequential legal battles. With 35 years of practice, he has built a reputation as one of the entertainment industry's most sought-after litigators, handling cases for clients including Britney Spears, Steven Spielberg, Keanu Reeves, Julia Louis-Dreyfus and Pinterest.

Rosengart's path to legal stardom began with athletic ambitions and evolved through government service. "I was a competitive athlete and as legendary litigator Edward Bennett Williams famously said, litigation is like 'contest living,'" Rosengart said. "Once it became clear I was not going to make it to the NBA, being a litigator was a great fallback and outlet for my competitive spirit."

His early career was shaped by an extraordinary mentor: late U.S. Supreme Court Justice David H. Souter, for whom he clerked on the New Hampshire Supreme Court before Souter's elevation to the higher court. The relationship profoundly influenced Rosengart's approach to law. "He was a giant in the law, of course -- brilliant, kind and decent, and he is sorely missed, especially in these polemical times," Rosengart said. "I think of him pretty much every day, in connection with both life and the practice of law."

After his clerkship, Rosengart served as an assistant U.S. attorney with the Justice Department, developing prosecution skills that would later prove invaluable in his private practice. His transition to entertainment law allowed him to merge legal expertise with personal passion.

"I was always an avid consumer of art -- books and film in particular," Rosengart said. "The arena of entertainment litigation allowed me to combine the skills I learned as an assistant U.S. attorney with the Justice Department with my interest in arts and entertainment."

Recent high-profile victories demonstrate Rosengart's range and tenacity. He successfully defended actor Sean Penn's charitable organization CORE against federal labor charges, securing a complete dismissal after trial. Community Organized Relief Effort, 31-CA-
272228 (NRLB, filed Feb. 3, 2021).

In March 2025, Rosengart obtained an emergency injunction for Meta Platforms against a former executive's unauthorized memoir, halting her book tour mid-stream.

Perhaps most notably, he freed Britney Spears from her 13-year conservatorship in 2021 and concluded all related litigation last summer. Re: the Conservatorship of the Person and Estate of Britney Jean Spears, BP108870 (L.A. Super. Ct. filed Feb. 1, 2008).

"It was especially rewarding, after several protracted court battles, beginning with suspending her father after a contentious court hearing and thereby winning her freedom from an oppressive 13-year conservatorship in 2021, to bringing all outstanding litigation against Britney Spears to an end last summer," Rosengart said. "Britney is an icon, and I'll always be proud of our transformative work together."

Rosengart acknowledged the unique pressures of his practice. "The nature of my clientele and docket right now is very high profile, which can present another challenging dimension to already-challenging cases involving evolving and complex areas of the law."

Despite representing Hollywood's elite, Rosengart maintains that his profession serves a higher purpose. "Although we're living in a time when lawyers, and sometimes the law, are under siege, I always believed being a lawyer was an honorable profession, providing an opportunity to help individuals and even potentially society."