Gregory Joseph Slavonic is an American government official and retired U.S. Navy officer. He has served as Acting Under Secretary of the Navy from April 24, 2020 to January 20, 2021. He served as the 18th United States Assistant Secretary of the Navy for Manpower and Reserve Affairs (ASN M&RA) from June 11, 2018 to January 20, 2021. Secretary Slavonic retired as a one-star rear admiral serving 34 years in the United States Navy and the Navy Reserve.