Colin Hackett Kahl is an American political scientist who served as under secretary of defense for policy in the Biden administration from April 28, 2021, to July 17, 2023.

[2][3][4][5] In the Obama administration, Kahl was involved in the negotiations of the Joint Comprehensive Plan of Action, commonly known as the Iran nuclear deal.

[8] Under his advisors Robert Jervis and Jack Snyder, Kahl's doctoral thesis was entitled States, Scarcity, and Civil Strife in the Developing World [Kenya].

From 2005 to 2006, he was a Council on Foreign Relations International Affairs Fellow, working on stability operations policy at the Department of Defense.

[16][17] In May 2018, it was revealed that aides to U.S. President Donald Trump had contracted with the Israeli private intelligence firm Black Cube to find evidence to support unsubstantiated and false claims that Kahl was being enriched by Iran lobbyists and that either he or deputy national security advisor Ben Rhodes were cheating on their wives.

His nomination was subject to controversy in the Senate, with the Republican caucus unanimously opposing his confirmation due to his support for the Iran nuclear deal, as well as for his criticisms of Trump administration policies.