Gilbert Owen Nations (1866–1950) was an American lawyer and judge from Washington, D.C. who campaigned against Roman Catholicism in the United States.

He was also a professor of Roman and Papal law at American University in Washington, D.C. Born in Perry County, Missouri in 1866, Nations only had 27 months of public schooling before dropping out and studying on his own.

He received a bachelor's degree from National Normal University of Lebanon, Ohio in 1890; and a master's in philosophy from Hiram College in 1900.

Nations served as a probate judge in St. Francois County, Missouri.

He moved to Washington, D.C. in 1916., and in 1919 received a Ph.D. from American University, one of the first issued by that institution.