John Thomson Mason (May 9, 1815-March 28, 1873) was a U.S. Congressman from Maryland, representing the sixth district from 1841 to 1843. Born at the Montpelier estate near Hagerstown, Maryland, Mason was educated by a private tutor and graduated from Princeton College in 1836. He studied law, was admitted to the bar, and commenced practice in Hagerstown in 1838.
He later served as a member of the Maryland House of Delegates in 1838 and 1839, and was elected as a Democrat to the Twenty-seventh Congress, serving one term from March 4, 1841 to March 3, 1843. He was a judge of the Maryland Court of Appeals from 1851 to 1857, and afterwards a collector of customs at Baltimore, Maryland from 1857 to 1861. He moved to Annapolis, Maryland, where he died. He is interred in Rose Hill Cemetery of Hagerstown.
