David Brock is an American liberal political consultant, author, and commentator who founded the media watchdog group Media Matters for America. He has been described by Time as "one of the most influential operatives in the Democratic Party".

Brock began his career as a right-wing investigative reporter during the 1990s. He wrote the book The Real Anita Hill and the Troopergate story, which led to Paula Jones filing a lawsuit against Bill Clinton. In 1997 he switched political sides, aligning himself with the Democratic Party and in particular with Bill and Hillary Clinton.

In 2004, he founded Media Matters for America, a non-profit organization which describes itself as a "progressive research and information center dedicated to comprehensively monitoring, analyzing and correcting conservative misinformation in the U.S. media". He has since also founded super PACs called American Bridge 21st Century and Correct the Record, has become a board member of the super PAC Priorities USA Action, advised The 65 Project, and has been elected chairman of Citizens for Responsibility and Ethics in Washington (CREW). Brock left Media Matters in November 2022. After leaving Media Matters, he founded Facts First USA, a 501(c)(4) group designed to counter Republican-led congressional investigations.

David Brock was born in Hackensack, New Jersey, and was adopted by Dorothea and Raymond Brock. He has a younger sister, Regina, who was also adopted. Brock was raised Catholic. His father, whom Brock has described as "a Pat Buchanan conservative", was a marketing executive.

Brock grew up in Wood-Ridge, New Jersey, where he went to Our Lady of the Assumption School, and later attended Paramus Catholic High School in Paramus, New Jersey. During his sophomore year of high school, Brock's family moved to the Dallas, Texas, area where Brock attended Newman Smith High School. Brock became editor of his high school newspaper, which he says he "fashioned into a crusading liberal weekly in the middle of the Reaganite Sunbelt".

Brock attended the University of California, Berkeley, where he graduated with a B.A. in history in 1985. He also worked as a reporter and editor for The Daily Californian, the campus newspaper. Brock arrived at college as a liberal Democrat, but at Berkeley he was "repelled by the culture of doctrinaire leftism" and turned to the political right. The turning point came with a column supporting the US invasion of Grenada that he wrote for The Daily Californian and that led to demands he resign from the newspaper staff. "I thought it was McCarthyism of the left", Brock later said. "I thought it was extremely intolerant." He then founded a neoconservative weekly, the Berkeley Journal.

While he was at Berkeley, Brock contributed an op-ed to The Wall Street Journal entitled "Combating Those Campus Marxists". It drew the attention of John Podhoretz, who at the time was the editor of Insight on the News, a weekly newsmagazine published by The Washington Times. Podhoretz flew Brock to Washington, D.C. for an interview and hired him as a writer of the Insight on the News. A job Brock took up in 1986. After working at Insight on the News, Brock spent some time as a fellow at the Heritage Foundation.

In March 1992, in a 17,000-word article for The American Spectator, Brock challenged the claims of Anita Hill, who had accused Clarence Thomas of sexual harassment. Shortly thereafter Brock became a full-time staff member at that publication. In 1993, Brock expanded his article into a book, The Real Anita Hill. Brock's description of Hill in the book as "a bit nutty and a bit slutty" was widely quoted.