The Under Secretary of Defense for Policy is a high level civilian official in the United States Department of Defense. The Under Secretary of Defense for Policy is the principal staff assistant and adviser to both the Secretary of Defense and the Deputy Secretary of Defense for all matters concerning the formation of national security and defense policy. The position is considered the number three office in the Department of Defense, after the Secretary of Defense and Deputy Secretary of Defense.
The Office of the Under Secretary of Defense for Policy is the principal staff element of the Secretary of Defense in the exercise of policy development, planning, resource management, fiscal, and program evaluation responsibilities.