John Alexander McNair (June 8, 1800 – August 12, 1861) was an American teacher and congressman representing Pennsylvania's fifth district for two terms from 1851 to 1855.
He established a boys school in the village of Abington, Pennsylvania.
He served as chairman of the United States House Committee on Manufactures during the Thirty-third Congress.
McNair settled on a plantation in Prince William County, Virginia, near Gainesville.
This article about a member of the United States House of Representatives from Pennsylvania is a stub.