Isaac Southard (August 30, 1783 - September 18, 1850) was an Anti-Jacksonian member of the United States House of Representatives from 1831 to 1833, representing New Jersey at-large.
A son of Henry Southard, Isaac Southard was born in the city of Basking Ridge in Somerset County, New Jersey. He had a brother, Samuel Lewis Southard. Southard was educated at the classical school of his city, and engaged in the general merchandise business until 1814.
Southard was elected as an Anti-Jacksonian to the Twenty-second United States Congress, and began his term on March 4, 1831. He did not succeed in his bid for reelection, and his term ended on March 3, 1833.
After his time as State Treasurer, Southard lived in Trenton, NJ for several years before moving to Somerville, NJ, where he lived until his death on September 18, 1850. He was interred in Somerville's old cemetery.