Triplanetary was a science fiction board wargame published by Game Designers' Workshop in 1973. It was a simulation of space combat within the solar system in the early 21st Century. The game was designed by Marc W. Miller and John Harshman as part of a series to be named "The Stars! The Stars!". The game is loosely taken from SF novels and short stories of the 1930’s, 40’s and 50’s - - particularly Heinlein . A second edition of the game was issued in 1981. In 1989, Steve Jackson acquired the rights to the game, with ambitions to release a new version of the game in 1991 that would tighten up a number of rules to improve play. Although a draft version was created, a new edition was never released.
The game consisted of a 16-page book of rules (with four additional pages of errata and clarification); a hex map of the inner solar system; a clear acetate overlay for the map, a grease pencil, a set of cardboard counters representing the various spaceships, and a 6-sided die. (The replacement game parts sold for US$6.80 in 1973.) The game scenarios typically allowed for two players, although some allowed for more players.
The map includes the Sun, Mercury, Venus, Earth and its Moon, Mars, part of the Asteroid belt, and Jupiter, along with the four largest Jovian moons. There were also hexes for two of the largest asteroids, and for a secret asteroid base. The map scale is 9.3 million miles across, so that the placement of the moons is entirely unrealistic; they were situated primarily for game play purposes and not for accuracy.