Nancy Eileen McEldowney (born October 6, 1958) is an American academic and diplomat who served as the national security advisor to Vice President Kamala Harris from January 20, 2021 to March 21, 2022. She was previously a career Foreign Service officer, served as United States ambassador to Bulgaria (2008–2009), and was director of the Foreign Service Institute from February 2013 until June 2017.