The Corsaireans were a humanoid species, often adversarial to the United Federation of Planets. (Starship Deimos: "Diplomatic Relations"; Starship Tristan: "Pride and Prejudice"; Starship Webster: "Opportunity")
The Corsaireans first encountered inhabitants of the planet Sodainya in the mid-2250s. ("Opportunity")
Captain Sian Gabriel and the officers and crew of the USS Deimos were assigned to assist with negotiations of a peace treaty with the Corsaireans in 2301. ("Diplomatic Relations")