The Vestios system is a star system, proximate to Starfleet Starbase 3. It is the home system to the Vestians, who had settled several of the system's planets. The system is ruled by a Vestian Council.
There had been numerous conflicts between the Vestians and the Federation in the early years of the 23rd century. A treaty between the two in the 2210s ensured peace between the two for several years. In 2220, a civil war broke out within the Vestios system, involving rebels on Vestios II. These rebels attacked Federation ships, apparently in an effort to involve the Federation in the fighting. Toward the end of the war, a Starfleet ship patroling the border, the USS Aldrin, did destroy a rebel ship, and fired on an official military vessel. The Vestians opted to overlook these instances to avoid an interstellar incident. The Vestians became members of the Federation in 2310. Ambassador Spock attended a conference on Vestios Prime in 2320 to mark the tenth anniversary of their membership. (TOS novel: Burning Dreams)