SimMars was a strategy game in development at Maxis around the same time as the release of the wildly popular Maxis game, The Sims. A trailer for the game was included on the SimCity 3000 CD. From the trailer, the premise of the game seemed to be a manned mission to the planet, Mars, followed by a terraforming and colonization scenario, typical of the Maxis world-building game style. The game presumed to be an integration of previous Maxis titles presented in 3D, possibly including elements of SimEarth, SimLife, and SimCity.

As of May 12, 2000, Maxis has stated that "SimMars is on hold and we do not have staff at Maxis currently working on the game. With the phenomenal success of The Sims, we've decided to move resources to support that franchise as well as other titles that we haven't even announced yet." [1]

One can assume that this project was placed even farther on the back burner by the release of subsequent expansion packages to The Sims, SimCity 4, and The Sims 2 and its related expansions.

Various fansites of SimCity 4 have made projects devoted to creating Martian structures into their games, using the Building Architect Tool. It is not known if Maxis will turn to them for their help in getting the SimMars up and running.