Isaac Southard (30 August 1783-18 September 1850) was a member of the US House of Representatives (NR-NJ AL) from 4 March 1831 to 3 March 1833, succeeding Samuel Swan and preceding William N. Shinn. Born in Basking Ridge, the son of Henry Southard and brother of Samuel L. Southard, he worked as a merchant before serving in Congress and later as state treasurer from 1837 to 1843.