Aaron Klein (Hebrew: אהרון קליין; born 1979) is an American-Israeli conservative political commentator, journalist, strategist, bestselling author, and senior advisor to Prime Minister Benjamin Netanyahu. He served as campaign manager for several of Netanyahu's election campaigns and chief strategist for Netanyahu's 2020 election campaign that resulted in a rotating unity government with Netanyahu at the helm and his 2022 campaign in which Netanyahu won a full-term. Klein was Netanyahu's full-time strategic advisor in government from 2020 to 2021, during the period Netanyahu was prime minister of Israel's 36th government and he serves as a strategic advisor to Netanyahu during Israel's 37th government.

Klein played a role in Donald Trump's 2016 presidential campaign. He was previously an American weekend radio talk show host, author, and senior reporter and Middle Eastern bureau chief for Breitbart News and a weekly columnist for The Jewish Press.

Klein grew up in Philadelphia and graduated from Torah Academy Boys High School. In his book Schmoozing with Terrorists, Klein describes his upbringing: "I was a Talmud-studying Modern Orthodox Jew. I attended Jewish religious schooling my entire life from religious elementary school until college. I came from a tight-knit orthodox Jewish community."

At Yeshiva University in New York City, Klein edited the undergraduate bimonthly student newspaper The Commentator and changed his major from biology to English upon becoming editor. "After determining that the publication was decidedly underwhelming in journalistic ambition—'a glorified synagogue newsletter,' Klein called it—he tried to up the paper's metabolism by publishing a series of articles that were highly critical of the school administration," according to a book by New York Times reporter Jeremy Peters.

Articles published in The Commentator regarding events such as use of an eight-million-dollar gift to the school and the removal of a secretary, written while Klein was a co-editor in chief, allegedly caused the school administration to remove some issues from circulation. This prompted the paper's editorial board to threaten to sue the university, generating national media attention. Yeshiva University later signed a contract with Klein in which it agreed to discontinue the practice and reimburse The Commentator for the confiscated issues.

In 2019, Klein advised Israeli Prime Minister Netanyahu while the premier was preparing a public campaign against the Israeli attorney general's decision to indict him.

Klein was chief strategist for Netanyahu's December 2019 Likud leadership primary in which Netanyahu scored a landslide victory.

Klein then served as chief strategist for Netanyahu's third successive general election after two previous elections failed to produce a clear majority government. Netanyahu's Likud party won more votes than any party in Israeli electoral history, with Likud crediting Klein's strategy for historic turnout from its voters. At his campaign's nationally televised "victory" event, Netanyahu publicly credited Klein with his victory in the March 2020 election, which produced a unity government in which Netanyahu would serve as prime minister for 18 months.