IMHO.

Free games like Terraforming Mars

Below are 8 free-to-play Steam games similar to Terraforming Mars, ranked by player overlap and content similarity. No purchase or Steam login required to view the list. Every pick is a full free-to-play title — not a demo, trial, or time-limited giveaway. imho.run's catalogue refreshes daily, so newly free or newly popular titles surface here without manual editing.

Want the full alternatives list (paid + free + Steam Deck + cheaper picks)? See the parent games like Terraforming Mars page.

Ranked picks

  1. 1
    The Lab — Steam game cover

    The Lab

    Free-to-play alternative to Terraforming Mars — no purchase or trial window.

    Welcome to The Lab, a compilation of Valve’s room-scale VR experiments set in a pocket universe within Aperture Science. Fix a robot, defend a castle, adopt a mechanical dog, and more. Still not sold? It’s free!

    2016Free To PlayFreeFree to playSimilar games →
  2. 2
    Die in the Dungeon: Origins — Steam game cover

    Die in the Dungeon: Origins

    Free-to-play alternative to Terraforming Mars — no purchase or trial window. Shares Strategy with Terraforming Mars.

    Fight your way through a mysterious dungeon in this deck-building, turn-based roguelike game where you don't use cards, but DICE! Deal with enemies by combining dice on your board, boost their effects with magical relics, and discover the story behind Die in the Dungeon!

    2023StrategyIndieRPGFreeDeck VerifiedFree to playSimilar games →
  3. 3
    Jigsaw Puzzle Dreams — Steam game cover

    Jigsaw Puzzle Dreams

    Free-to-play alternative to Terraforming Mars — no purchase or trial window.

    Beautiful Multiplayer Jigsaw Puzzle game where you can design the room you play in!

    2021IndieFree To PlayCasualFreeDeck PlayableFree to playSimilar games →
  4. 4
    The Last Sovereign — Steam game cover

    The Last Sovereign

    Free-to-play alternative to Terraforming Mars — no purchase or trial window. Shares Strategy with Terraforming Mars.

    Explore a world torn between armies of lust and purity in which everything is more complex than it seems, deciding the fate of nations through might, politics, and finance. Every decision matters in an intricate saga that tracks thousands of variables.

    2025StrategyIndieAdventureFreeDeck VerifiedFree to playSimilar games →
  5. 5
    Counter-Strike 2 — Steam game cover

    Counter-Strike 2

    Free-to-play alternative to Terraforming Mars — no purchase or trial window.

    For over two decades, Counter-Strike has offered an elite competitive experience, one shaped by millions of players from across the globe. And now the next chapter in the CS story is about to begin. This is Counter-Strike 2.

    2012ActionFree To PlayFreeDeck PlayableFree to playSimilar games →
  6. 6
    Dota 2 — Steam game cover

    Dota 2

    Free-to-play alternative to Terraforming Mars — no purchase or trial window. Shares Strategy with Terraforming Mars.

    Every day, millions of players worldwide enter battle as one of over a hundred Dota heroes. And no matter if it's their 10th hour of play or 1,000th, there's always something new to discover. With regular updates that ensure a constant evolution of gameplay, features, and heroes, Dota 2 has taken on a life of its own.

    2013ActionStrategyFree To PlayFreeDeck PlayableFree to playSimilar games →
  7. 7
    Tom Clancy's Rainbow Six Siege — Steam game cover

    Tom Clancy's Rainbow Six Siege

    Free-to-play alternative to Terraforming Mars — no purchase or trial window.

    Rainbow Six® Siege is the reference in tactical team shooters, where elite strategy and execution triumph. Enjoy free access to Quick Match, Unranked, and Dual Front game modes with a selection of operators.

    2015ActionFree To PlayFreeFree to playSimilar games →
  8. 8
    SCP: Secret Laboratory — Steam game cover

    SCP: Secret Laboratory

    Free-to-play alternative to Terraforming Mars — no purchase or trial window.

    Deep within a secure underground facility, a sudden containment breach allows many of the secured anomalies to escape from their chambers. Assist the Foundation in re-securing the facility, help the Insurgency in their goal to capture it, or wreak havoc as an SCP in a frantic bid to escape.

    2017ActionIndieRPGFreeDeck PlayableFree to playSimilar games →