Richard Merrill Mills Jr. (born February 23, 1959) is an American diplomat who serves as the United States deputy ambassador to the United Nations. He served as the U.S. Chargé d'Affaires and Acting Permanent Representative to the United Nations between January 20, 2021, and February 24, 2021, when Linda Thomas-Greenfield became ambassador. In July 2022, he was announced as the nominee to serve as the United States ambassador to Nigeria. He previously served as the U.S. Chargé d'Affaires for Canada.