Dennis Mark Prager (/ˈpreɪɡər/; born August 2, 1948) is an American conservative radio talk show host and writer. He is the host of the nationally syndicated radio talk show The Dennis Prager Show. In 2009, he co-founded PragerU, which creates content advocating capitalism and promoting conservative viewpoints on various political, economic, and sociological topics.

His initial political work, starting in 1969, focused on the Refuseniks, Soviet Jews who were denied permission to emigrate. He gradually began offering more and broader commentary on politics.

Dennis Mark Prager was born on August 2, 1948, in Brooklyn to Hilda (née Friedfeld; 1919–2009) and Max Prager (1918–2014), the latter the son of Polish Jewish immigrants. Prager and his brother, Kenneth Prager, were raised in a Modern Orthodox Jewish home. He attended the Yeshiva of Flatbush in Brooklyn, New York, where he befriended Joseph Telushkin.

Prager attended Brooklyn College, where he double majored in anthropology and history, and received a B.A. in 1970. He became a fellow at the Columbia University School of International and Public Affairs and attended there from 1970 to 1972, while he also took courses at the University of Leeds. After he left graduate school, Prager left Modern Orthodoxy but maintained many traditional Jewish practices; he remains religious. Prager holds an honorary Doctor of Laws from Pepperdine University.

In 1969, while he was studying in England, he was recruited by the government of Israel to smuggle Jewish religious items into the Soviet Union and smuggle out names of Jews. When he returned the next year, he was in demand as a speaker on repression of Soviet Jews; he earned enough from lectures to travel, and visited around sixty countries. He became the national spokesman for the Student Struggle for Soviet Jewry.

The start of Prager's career overlapped with a growing tendency among American Jews, who had been staunchly liberal, to move toward the center and some to the right, driven in part by the influx of Jews from the Soviet Union. In 1975, Prager and Telushkin published an introduction to Judaism intended for nonobservant Jews: The Nine Questions People Ask About Judaism, which became a bestseller. Among the questions addressed in the text were: how does Judaism differ from Christianity, and can one doubt the existence of God and still be a good Jew, and how do you account for unethical but religious Jews?

Prager ran the Brandeis-Bardin Institute from 1976 to 1983; Telushkin worked with him there. It was Prager's first salaried job. He soon earned a reputation as a moral critic denouncing secularism and narcissism, both of which he said were destroying society; some people called him a Jewish Billy Graham.

In 1982, KABC (AM) in Los Angeles hired Prager to host its Sunday night religious talk show Religion on the Line, which got top ratings and eventually led to a weekday talk show. He and Telushkin published another book in 1983, Why the Jews? The Reason for Antisemitism.