Mark S. Zaid is an American lawyer in Washington, D.C., whose practice centers on national security law, government secrecy, security clearances and the Freedom of Information Act. His clients have included intelligence and military officers, defense contractors, whistleblowers and journalists, and by his own account he has represented victims of anomalous health incidents for about fifteen years. His link to the UAP subject is indirect: disclosure-focused accounts such as Disclosure Party regularly repost his commentary on secrecy, whistleblowers and those incidents, but the cases he publicizes concern those issues rather than UAP.

Born in 1967 in Manhasset, New York, Zaid earned a bachelor's degree at the University of Rochester in 1989 and a law degree from Albany Law School in 1992, where he was an associate editor of the Albany Law Review. In 1998 he founded the James Madison Project, a nonprofit devoted to reducing government secrecy through FOIA work and support for whistleblowers, and in 2017 he co-founded the legal organization Whistleblower Aid with former State Department whistleblower John Tye. He also teaches national security and intelligence law as an adjunct professor at Johns Hopkins University and sits on the board of trustees of Albany Law School.

His litigation has ranged widely. He sued Libya over the 1988 bombing of Pan Am Flight 103, litigation that ended in a $2.7 billion settlement, and in 2004 he won an injunction that halted the Defense Department's mandatory anthrax vaccination program for two years. His FOIA suits have pursued the FBI's files on the D.B. Cooper hijacking, with author Thomas Colbert, and on the Monkees' Micky Dolenz. In 2019 he was part of the legal team, led by Andrew Bakaj, that represented the intelligence community whistleblower whose complaint led to President Donald Trump's first impeachment.

That case led to a clash with the Trump administration in its second term. The president moved to revoke his security clearance in February 2025, and Director of National Intelligence Tulsi Gabbard announced the revocation that March; Zaid, who had held a clearance for nearly 25 years, called it "petty retaliation because I represent my clients effectively." He challenged the decision in federal court, won a preliminary injunction in December 2025, and reported in January 2026 that he could again access classified information.

The incidents popularly called Havana syndrome dominated his public work in 2026. When Gabbard in June rescinded two Biden-era intelligence assessments that had judged a foreign adversary very unlikely to be responsible, he wrote that it was "what we have been working towards for over a decade," and his firm kept suing her office and the CIA under FOIA for the underlying reports. He said his firm represents several federal employees who suffered such incidents inside the United States, and in September a federal court in Washington allowed his clients to argue for discovery from the State Department on whether hostile foreign actors were responsible. After some fifteen years of such cases, Zaid is among the lawyers most closely identified with government personnel who say they were injured in the line of duty and denied answers by their agencies.