Roswell Foster Magill (November 20, 1895 – December 17, 1963) was an American tax lawyer and Treasury Department official.

As Treasury Secretary Andrew W. Mellon's top lawyer, he helped make the case for major tax reform in 1924.

In 1927 he left public service for a faculty post at Columbia Law School, where he introduced a class on federal income taxation.

[1] He supervised preparation of the Tax Revision Studies, a series of reports on every aspect of federal taxation.

Also, he was hired by prestigious New York law firm Cravath, Swaine & Moore in 1943, as a rare lateral partner.