Jack Dyer Crouch II (born July 1, 1958) is an American diplomat and national security adviser.

From 1990 to 1992, he served in the administration of U.S. President George H. W. Bush as the Principal Deputy Assistant Secretary of Defense for International Security Policy.

He was appointed Deputy National Security Advisor by U.S. President George W. Bush in March 2005, serving until May 2007.

Ambassador to Romania (from 2004 to 2005) and as the Assistant Secretary of Defense for International Security Policy (from 2001 to 2003), among other positions in government under Republican administrations.

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