David Joel Horowitz (1939–2025) was an American conservative writer, political activist, and commentator, widely recognized as a key figure in the network of conservative charities and the founder of the David Horowitz Freedom Center. Born into a Jewish family of Communist Party members in Queens, New York, he was raised in a 'red-diaper' environment and initially embraced New Left radicalism. He earned a BA from Columbia University in 1959 and an MA from UC Berkeley in 1961. During the 1960s, he immersed himself in radical politics, living in London where he worked for the Bertrand Russell Peace Foundation and associated with Marxist historian Isaac Deutscher. After returning to the U.S. in 1968, he co-edited the influential New Left magazine Ramparts and collaborated with Peter Collier on best-selling biographies of American dynasties.

A pivotal shift in his ideology occurred in the late 1970s when he rejected Marxism, prompted by his horror over the murder of a Black Panthers' bookkeeper he had helped place. This event marked his transition from radicalism to staunch modern conservatism, becoming a prominent anti-communist and counter-jihad advocate. In 1988, Horowitz and Collier co-founded the Center for the Study of Popular Culture, which evolved into the David Horowitz Freedom Center (DHFC) in 2006. The DHFC operates as a think tank coordinating a donor network and focuses on anti-leftist and anti-Islamist causes, promoting pro-Israel viewpoints and advancing its mission through publications, events, media, education, and funding initiatives such as Jihad Watch.

Horowitz edited FrontPage Magazine, launched Discover the Networks—a database tracking left-wing figures—founded Students for Academic Freedom, and created the magazines Heterodoxy and TruthRevolt. His platforms featured figures like Walid Shoebat. An author of over 50 books, including his memoir Radical Son (1997), chronicling his ideological journey, and The Professors, critiquing leftist academics, Horowitz became a fierce debater, petition organizer, and mentor in conservative circles. He was known for his critiques of the left, campaigns against liberalism, Islam, and progressive education, and for promoting anti-Islam narratives and campus conservatism.

In his later years, Horowitz solidified his role as a conservative lightning rod and key architect in the 'shadow network' of conservative charities, funding activism against what he termed 'wokeness' and Islamist influences. Despite controversies over his inflammatory rhetoric and accusations of Islamophobia, he remained an influential figure until his death on April 29, 2025, leaving a legacy as a self-proclaimed 'former radical' who leveraged his past experience to critique the left.