Ratified February 7, 1795
The first amendment added after the Bill of Rights, prompted directly by a Supreme Court case (Chisholm v. Georgia, 1793) the states didn't like. It bars federal courts from hearing lawsuits against a state brought by a citizen of a different state or of a foreign country — an early expression of "state sovereign immunity."
The Judicial power of the United States shall not be construed to extend to any suit in law or equity, commenced or prosecuted against one of the United States by Citizens of another State, or by Citizens or Subjects of any Foreign State.