Roswell Foster Magill (November 20, 1895 – December 17, 1963) was an American tax lawyer and Treasury Department official. He was one of the most important tax officials of the 1930s and one of the leading tax experts. After briefly serving as special tax advisor to Treasury Secretary Henry Morgenthau in the early 1930s, Magill was nominated by President Roosevelt to become Under Secretary of Treasury in 1937. He supervised preparation of the Tax Revision Studies, a series of reports on every aspect of federal taxation.