Traveller is a science fiction roleplaying game, originally released in 1977 by Game Designers’ Workshop, and written primarily by Marc Miller. There are numerous editions, as well as versions using different game mechanics, but in its “true” form Traveller uses two six-sided dice for most activities and task resolution.
Classic Traveller is generally considered to be the original 1977 edition, the 1981 printing with slight revisions, and various versions of those (The Traveller Book and the Traveller Facsimile Edition).
Mongoose Publishing is the current owner of Traveller.