Civilization (series)!

Freeciv is an open-source, turn-based strategy game based on Civilization II. Inspired by the history of human civilization, the game commences in prehistory and your mission is to lead your tribe from the stone age to the space age...

Widelands is a free, open source real-time strategy game with singleplayer campaigns and a multiplayer mode. The game was inspired by Settlers II™ (© Bluebyte) but has significantly more variety and depth to it. Still, it is easy to get started through playable tutorials.

Classic turn-based strategy game with two armies fighting against each other. Challenge yourself in campaign against AI or hot-seat battle with a friend. Using easy map editor you can create any imaginable scenario to play and share online for others to discover!Each 32x32 sprite was handcrafted in gorgeous, 32 colour pixel art. Original soundtrack was made on Access Virus C and Korg Electribe. Sound effects were made on real GameBoy hardware. Game is open-source and runs smoothly thanks to Godot Engine. »

FreeCol is a 4X video game, a clone of Sid Meier's Colonization. While remaining faithful to the original in terms of mechanics and gameplay, FreeCol sports a new set of redesigned graphics. Moreover, in addition to the classical Colonization rules, it features an additional ruleset that incorporates ideas that didn't make it to the final version of Meier's game, requests by fans and original concepts like new European players with new national bonuses.

Play in a randomly generated world or make your own with the map editor. Go to war with 26 different civilisation with their own unique abilities and fight them with 54 different units ranging from primitive warriors to state of the art mechs. Or co-operate with them using the diplomacy and trade routes systems. Or improver your own lands with 14 terrain improvements, 81 technologies and 82 unique buildings. Allow the AI to control your opponents or play against others with a game translated into 11 different languages. And all the while you can receive information from the mini map and your civilisation's score. And once you are victorious you can save your game onto your device, dropbox or NewSoftVision's own servers. »

Free (as in freedom) open-source RTS http://alternativeto.net/software/age-of-empires-iii/ engine. Written from scratch in C++14 and Python, using OpenGL + GLSL.

C-evo is a freeware empire building game for Windows

UniWar is a turn-based strategy game where players battle it out on the field with units of differents races, building bases and using the terrain to overcome their opponents towards victory. Several modes are available along with many maps to play.

Fulfill Your Quest For Global Domination

Here comes the Golden Age of Civilizations, a semi turn-based MMO strategy game, inspired by but not following the classic games of the genre, such as Age of Empires, Civilization and Rise of Nations; mixed up with MMO capability and flavored with the best parts of other good online games.

A board game for the web!

From legendary game designer Brian Reynolds (Civilization II, Rise of Nations), DomiNations is an epic new strategy game of exploration, advancement, and conquest. Lead your Nation to ultimate victory throughout all of human history – from the Stone Age to the Space Age! Build your capital city, pick your Nation from among the greatest civilizations of the world, and defeat rival Alliances to become the most powerful ruler on the planet!

Ironfell is a time travel themed massive multi-player online real time strategy game. Travel back in time to plunder resources from the past, re-build your empire and conquer the stars.