Free & Open Source Sci-Fi Games
521 free, open-source sci-fi games — real clones and remakes you can download, inspect the source of, and modify.
Halted
Clone of Star Ruler 2
A massive-scale 4X/RTS set in space, officially open-sourced by original developer Blind Mind Studios.
Platforms:WindowsLinux
Stars1,528
Updated3 years ago
LicenseUnknown
Release2018
Genre: Real-Time Strategy
Theme: Sci-Fi
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Clone of Cave Story
A from-scratch reimplementation of the Cave Story engine with quality-of-life improvements, requiring the original game's data files.
Halted
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Clone of Star Wars: Knights of the Old Republic
An open-source reimplementation of BioWare's Aurora engine, aiming to run NWN through Dragon Age II — no game has full gameplay yet.
Halted
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Clone of Natural Selection
An open-source arena shooter blending FPS combat with RTS base-building, inspired by mods like Natural Selection.
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Clone of Unreal Tournament
A reimplementation of Unreal Engine 1 aiming to run the original Unreal and Unreal Tournament using your own game files.
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Active
Clone of Hard Vacuum
An open-content OpenRA real-time strategy game based on Daniel Cook's Hard Vacuum design, with online multiplayer and a map editor.
Platforms:WindowsLinuxOSX
Stars1,071
Updated1 month ago
LicenseGPL-3.0
Release2019
Genre: Real-Time Strategy
Theme: Sci-Fi
Active
Original game image
Original game imageClone of Master of Orion
FreeOrion is an open-source, turn-based 4X space empire game with scripting support for community-customized mechanics and content.
Platforms:WindowsLinuxOSX
Stars1,042
Updated1 month ago
LicenseUnknown
Release2015
Genre: Turn-Based Strategy
Theme: Sci-Fi
Halted
Clone of Duke Nukem II
A reverse-engineered, feature-complete reimplementation of Duke Nukem II in modern C++, with widescreen and controller support.
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Original game image
Original game imageClone of Quake 2
An enhanced, actively maintained Quake II client with widescreen, modern controller, and OpenGL 3.2 support.
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Clone of Doom
Crispy Doom is a limit-removing Doom source port with higher resolution, widescreen, and uncapped framerate, staying demo-compatible.
Halted
Clone of Another World
A readability-focused reimplementation of the Another World engine; needs the original PC DOS game data.
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Clone of Artemis: Spaceship Bridge Simulator
EmptyEpsilon is an open-source game that began as an Artemis Spaceship Bridge Simulator clone but has since diverged with new features.
Platforms:WindowsLinuxAndroid
Stars869
Updated2 months ago
LicenseGPL-2.0
Release2014
Genre: Simulation
Theme: Sci-Fi
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Active
Clone of Might and Magic VI: The Mandate of Heaven
An open-source Might & Magic VI-VIII engine reimplementation, currently able to play Might and Magic VII on modern systems.
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Clone of Total Annihilation
An open-source RTS with physical projectiles and smart units, built on the Spring Engine, similar to Total Annihilation.
Platforms:WindowsLinux
Stars827
Updated1 month ago
LicenseGPL-2.0
Release2013
Genre: Real-Time Strategy
Theme: Sci-Fi
Active
Active
Clone of Artemis: Spaceship Bridge Simulator
An open-source, Artemis-inspired multiplayer spaceship bridge simulator for Linux with Lua-scripted missions.
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Clone of Doom
DOOM Retro is a Windows Doom source port by Brad Harding since 2013, aiming for a dark, gritty, pixelated take on the classic game.
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Clone of Star Wars Jedi Knight: Dark Forces II
A function-by-function C reimplementation of Jedi Knight: Dark Forces II for Windows, macOS, Linux and more.
Stars760
Updated1 month ago
LicenseUnknown
Release2018
Genre: Fighting
Theme: Fantasy
Halted
Original game image
Original game imageClone of Return to Castle Wolfenstein
iortcw is a modernized baseline engine for Return to Castle Wolfenstein and its mods, with development now halted but still playable.
Active
Active
Clone of Space Station 13
A free multiplayer RPG remake of the cult-classic Space Station 13, rebuilt outside the original BYOND engine.
Halted
Original game image
Original game imageClone of Command & Conquer: Generals
An open-source rewrite of Command & Conquer Generals: Zero Hour, currently requiring the original game's binary.
Platforms:Windows
Stars690
Updated2 years ago
LicenseGPL-2.0
Release2017
Genre: Real-Time Strategy
Theme: Sci-Fi
Halted
Clone of Cave Story
A rewrite and port of the freeware game Cave Story for the Sega Mega Drive/Genesis.
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Original game image
Original game imageClone of Descent
A source port of Descent and Descent II that modernizes them for current PCs with OpenGL rendering and UDP multiplayer.
HaltedOriginal game image
Original game imageClone of Return to Castle Wolfenstein
Official id Software GPL source release of Return to Castle Wolfenstein's single-player code; game data isn't included.
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Clone of Freelancer
A C# and OpenGL reimplementation of Freelancer for Windows and Linux, requiring an existing Freelancer installation to run.
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Clone of X-COM: Apocalypse
An alpha reimplementation of X-COM: Apocalypse with modding, a skirmish mode and modern resolutions; it needs the original files.
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Clone of Tyrian
An open-source port of the DOS shooter Tyrian that includes the freeware game data and supports networked play.
