Isaiah David Hart (November 6, 1792 – September 4, 1861) was an American plantation owner, slaver, and the founder of Jacksonville, Florida.
Originally from Georgia, Hart took up arms against Spain in the Patriot Rebellion of 1812.
After moving to a location near the cow ford on the narrows of the St.
Johns River, he began platting the town in 1822, and later served as postmaster, court clerk, commissioner of pilotage, judge of elections, major in the local militia during the Seminole War, and as a Whig member of the Florida Territorial Senate.