Thomas Smith Grimké (September 22, 1786 – October 12, 1834) was an American attorney, author, orator and social activist.
Thomas Grimké was the second of fourteen children borne to jurist John Faucheraud Grimké, and Mary ("Polly"), daughter of Thomas and Sarah (Moore) Smith, of Charleston, South Carolina. He graduated from Charleston College, and entered the study of law under John Julius Pringle, then Attorney General of South Carolina, in 1804. He suspended his legal studies to enter Yale in the fall of 1805. After completing courses at Yale, Grimké expressed a desire to prepare for the ministry, but yielded to the wishes of his jurist father and was admitted to the bar in May 1809. Grimké practiced law in Charleston, South Carolina. In 1830, Grimké received an honorary degree of Doctor of Laws from Yale.
On 17 March 1827, Grimké advocated, in an address before the Bar Association of South Carolina, the codification of the laws of that state. He was a member of the State Senate in 1826-1830, and in 1828 made a speech in support of the federal government on the tariff question.
Grimké had a distinguished career in the Carolina courts. He is perhaps best known for the case of M'Cready v. Hunt, focusing on States Rights, which was brought before the South Carolina Court of Appeals in 1834. The case involved a "test oath" passed by the South Carolina legislature in November 1832. The oath required that members of the state militia pledge "faithful and true allegiance" to the State of South Carolina. The law was vague on the underlying and contentious issue of sovereignty, and did not specifically state whether allegiance to the state was superior to allegiance to the federal government. However, dispute over the oath immediately erupted. The "Nullifier" faction asserted that allegiance to states had precedence over allegiance to the federal government, while "Unionists" asserted that the federal government had primacy over all states.
Eventually, a legal case on the validity of the test oath reached the state Court of Appeals in Columbia. Attorney Robert Barnwell Rhett, of Beaufort, argued for the test oath with the support of state Governor Robert Y. Hayne. He was opposed by a trio of young Unionist attorneys, James L. Petigru, of Charleston, business attorney Abram Blanding, of Columbia, and Thomas S. Grimké. The June 2nd, 1834 decision from the three judges fell 2 to 1 for the Unionists. "Nullifiers" immediately called for the impeachment of the two jurists. "Nullifier" legislators responded to the decision by calling for a constitutional amendment to legalize the test oath and assert the primacy of allegiance to South Carolina.