Jonathan Karp (born April 2, 1964) is an American book editor, publisher, and writer. He was the publisher, president, and chief executive of Simon & Schuster where he led the company's flagship division. Karp also founded Twelve, an imprint at the Hachette Book Group, and was the editor-in-chief of Random House.

Karp was born to a Jewish family and raised in the Short Hills section of Millburn, New Jersey. His mother worked as a schoolteacher and his father served as chairman and chief executive officer at a bank. Karp graduated from Brown University in 1986, where he majored in American civilization and served as president and editor of the student publication, The Brown Daily Herald. He wrote his master's thesis on Herman Wouk's novels.

Karp wrote for The Washington Post in the mid-1980s, then worked as a reporter for The Providence Journal and the Miami Herald. He then relocated to New York City to pursue his interests in books and theatre.

Karp joined Random House in 1989 as an editorial assistant, and by 2000 he was serving as vice president and senior editor. In July 2000, he was promoted to the role of publisher of '@Random', the company's e-book branch, and eventually worked his way up to editor-in-chief of Random House. He worked for Random House for sixteen years, with one interruption; in 2000, he left the publisher to head producer Scott Rudin's office in New York (Scott Rudin Productions) as vice president of development. However, he returned to Bertelsmann several weeks later.

Karp then served as publisher and editor-in-chief of Twelve, an imprint he established within the Hachette Book Group in 2005, which publishes one book per month. Fifteen of Twelve's first thirty books appeared on The New York Times Best Seller list.

In mid 2010, Karp left Hachette to become Simon & Schuster's publisher, and was subsequently named president of the flagship division. On 29 May 2020, he became the CEO of Simon & Schuster. Karp was included in Publishers Weekly's 2022 list of 25 "book business change makers", or "seriously consequential individuals whose mark on the industry is indelible". In his role as chief executive, Karp testified in a 2022 antitrust trial filed by the Department of Justice to prevent Penguin Random House from acquiring Simon & Schuster.

In 2022, Simon & Schuster sold 900 autographed copies of Bob Dylan’s book of essays, “The Philosophy of Modern Song.” Accompanying each $600 book was a letter of authenticity signed by Karp, the publisher's chief executive, indicating that the books had been hand signed by Dylan. According to a New York Times article, when the books arrived, readers immediately noticed that the autographs appeared to have been machine generated by an auto pen. While Simon & Schuster initially denounced the “online rumors,” intense pressure led the publishing house to send out an “acknowledgment” that the autograph had been rendered “in a penned replica form.” Buyers were then provided a refund. Karp and Simon & Schuster declined further comment. Dylan later said "his decision to digitally sign" the books was an "error in judgment", according to the Los Angeles Times.

Karp is the longtime editor of John McCain; the two collaborated with Mark Salter on Faith of My Fathers (1999), Worth the Fighting For (2002), Why Courage Matters (2004), and The Restless Wave (2018).