Traveller was inspired by the success of Dungeons & Dragons, which had been released in 1974. Mark Miller realised there was scope for a science fiction roleplaying game with spaceships and technology and developed the Traveller game rules, with help from Frank Chadwick, John Harshman and Loren Wiseman. The game was released on 22 July 1977 by Game Designers' Workshop with a striking black cover.
It was an immediate bestseller, answering the demand for "Dungeons & Dragons but in space," as well as people who were interested in the idea of roleplaying games but not a classic fantasy setting. Traveller was also bolstered by the launch of the movie Star Wars just a few weeks earlier, which created a hunger for everything science fiction.
Traveller was originally a rules set without any setting material, but subsequent expansions introduced a far-future setting where humanity has colonised the stars with an FTL drive, but without FTL communications the various colonies and nations of humanity have splintered into small states, divided between different "strands" of humanity. Aliens exist in the setting but are mostly rare or extinct. Alternate SF settings for the game were created by fans and other creators.
An interview with Marc Miller at Dieku Games.
Traveller introduced innovations to the RPG space, including the idea of "life paths." Rather than characters being relative youngsters meeting in a bar and deciding to join forces (the standard D&D setup), Traveller characters are older and have usually had extensive training or education before deciding to become adventurers. Characters can be former soldiers, bureaucrats, medics, pilots or almost anything else the player can conceive of. Creating a character involves playing a mini-game of its own as players work out their heroes' backgrounds and their career. Infamously, it is possible for a character to die in character creation! This system also rewards extended service but also introduces penalty: the older a character is when they start the adventure, the more skills they have, but also the greater the possibility of injury or a degrading of skills due to old age.
Traveller also focused heavily on a skill system, a stalwart of every RPG apart from Dungeons & Dragons, which didn't really develop a skill system until 3rd Edition (earlier editions experimented with "proficiency" rules which tried to covers skills with a very broad brush). Most notably, this skill system allowed for a greater variety in resolving tasks and situations without combat. Traveller also emphasised its "social" skills to encourage roleplaying.
Traveller has been reissued in multiple editions since its original 1977 release: MegaTraveller (1987), Traveller: The New Era (1993), Marc Miller's Traveller (1996), GURPS Traveller (1998), Traveller d20 (2002), GURPS Traveller: Interstellar Wars (2006), Traveller Hero (2006), Mongoose Traveller 1st Edition (2008), Traveller 5.0 (2013), Mongoose Traveller 2nd Edition (2016) and Traveller 5.10 (2019).
The game is notable for using its own rule system, which relies heavily on six-sided dice rather than the plethora of different-sized dice favoured by D&D. However, over the years the game has been "ported" to other systems, including the D&D 3rd Edition "d20" system, the universal GURPS rules set and the Hero System. Players have also created homebrew variants based on other systems.
The Traveller setting has been used as the background for sixteen novels, published sporadically from 1993 to 2015. Surprising, only two video games have been developed from the setting: MegaTraveller 1: The Zhodani Conspiracy (1990) and MegaTraveller 2: Quest for the Ancients (1991), both from Paragon. The games were critically well-received and apparently successful, but no further video games based on the system have since appeared.
Traveller was a very forwards-thinking TTRPG when it was released and its influence on the genre remains very high. Here's hoping it carries on for many years to come.