Ian Joseph Brzezinski (born December 23, 1963) is an American foreign policy and military affairs expert.

He served as Deputy Assistant Secretary of Defense for Europe and NATO Policy from 14 May 2001 to 20 January 2005, under President George W. Bush.

He returned to the United States in 1995, and became Legislative Assistant for National Security Affairs to Senator William Roth.

After leaving the Defense Department, Brzezinski became a Principal at the consulting firm Booz Allen Hamilton, Inc., providing policy and technical advice to U.S. combatant commands and foreign clients.

He left Booz Allen Hamilton after five years, and now heads the Brzezinski Group, which provides similar services: " ... a strategic advisory firm serving U.S. and international commercial clients in the financial, energy, and defense sectors.