A consul is an official appointed by a government to reside outside the government's territory and oversee that government's interests and provide assistance to its citizens abroad.
In 2287, General Korrd was the Klingon consul to the Planet of Galactic Peace. Starfleet Operations also considered Federation representative St. John Talbot and Romulan representative Caithlin Dar as consuls. (Star Trek V: The Final Frontier)
In 2373, Captain Kathryn Janeway and Neelix dealt with a Tak Tak consul during a three-day trade mission, who later planned to destroy USS Voyager when he learned that it had been infested with macroviruses. (VOY: "Macrocosm")