Traveller by Mongoose Publishing, first edition, is an RPG primarily revolving around space and space travel released in 2007. Not to be confused with 2nd edition released in 2016.

Based on Classic Traveller by Game Designer's Workshop from 1977, Mongoose's version of Traveller attempts to retain the feel whilst giving the rules a more modern update. The core book is relatively setting-light but assumes that the game is taking place in Traveller's Third Imperium, where communication between stars is slow and space travel is potentially highly dangerous, leading to star-spanning empires with varying levels of technology, laws, and government styles from planet to planet.

Character creation uses a "lifepath" system, where players choose careers for their character and make skill and attribute checks to determine how they develop and what events they encounter, broken down into 4-year terms. Classic Traveller's death-during-character-creation rule is an optional rule.

The core book includes a limited selection of equipment and starship hulls, with rules for designing new spacecraft, whilst supplements provide extra gear and ship blueprints with floorplans.

The default setting and technology promote a campaign that is typically reminiscent of the Firefly TV series, with a group of Travellers flying between systems whilst taking on work from various patrons, trading, and keeping their ship maintained and supplied - typically whilst dealing with an expensive ship mortgage. Supplements provide expanded career choices and campaign options, often with additional rules to support different lifestyles, such as warship commanders or pirates and smugglers. Further supplements detail alien empires, which range from psionic humans to difficult-to-comprehend starfish-esque aliens.

Mongoose Traveller's 2nd edition was released in 2016, and goes under the mongoose-traveller-2 tag.