OpenCiv3

OpenCiv3 (formerly known by the codename “C7”) is an open-source, cross-platform, mod-oriented, modernized reimagining of Civilization III Conquests by the fan community. Built with the Godot Engine and C#, it has capabilities inspired by the best of the 4X genre and lessons learned from modding Civ III. Our vision is to make Civ III as it could have been, rebuilt for today’s modders and players: removing arbitary limits, fixing broken features, expanding mod capabilities, and supporting modern graphics and platforms. A game that can go beyond Civ III but retain all of its gameplay and content.

OpenCiv3 is under active development and currently in a pre-alpha state. It is a rudimentary playable game but lacking many mechanics and late-game content, and errors are likely. Keep up with our development for the latest updates and opportunities to contribute!

New Players Start Here: An Introduction to OpenCiv3 at CivFanatics

Connect with the community

NOTE:
OpenCiv3 Copyright (c) OpenCiv3 contributors

All content is the property of the respective authors. For more information regarding the authorship of content, see the applicable source repository logs and/or credits files in the respective directories.

OpenCiv3 seeks to be a mechanically compatible black-box reimplementation of Civilization III. No part or product of Civilization III ships with OpenCiv3. OpenCiv3 reimplements Civilization III gameplay using original code and media produced by the community, based on publicly available information and observations. OpenCiv3 provides the option to load media from the player’s own locally installed copy of Civilization III for a more faithful experience.

OpenCiv3 is not affiliated with or endorsed by civfanatics.com, Firaxis Games, BreakAway Games, Hasbro Interactive, Infogrames Interactive, Atari Interactive, or Take-Two Interactive Software. CIV and CIVILIZATION are registered trademarks of Take-Two Interactive Software, Inc. All trademarks are property of their respective owners.

October 2026: OpenCiv3 v0.3 Dutch 2 Has Been Released!

The OpenCiv3 team is pleased to announce the second release of the v0.3 “Dutch” milestone. This is a significant enhancement over the first “Dutch Preview 1” release, introducing many new features including the ability to win the game! Conquest and Domination victory types are available. Other highlights include our new title screen music in standalone mode; a greatly improved domestic advisor; expanded game setup options; and the introduction of unit bombardment, transport, and promotion mechanics. A local installation of Civilization III is still recommended for a more polished experience.

See the release announcement at CivFanatics for the full list of new features.

OpenCiv3 Dutch 2

OpenCiv3 Dutch 2 in standalone mode showing victory status

Download

Download the appropriate zip file for your OS from the Dutch 2 release

All official releases of OpenCiv3 along with more detailed release notes can be found on the GitHub releases page.

Install

System Requirements

64-bit Windows, Linux, or Mac OS. Other platforms may be supported in future releases.
Minimum hardware requirements have not yet been identified. Refer to Godot’s system requirements as a baseline. Please let us know if OpenCiv3 does not perform well on your system, or how it does on a particularly old system.
Currently the OpenCiv3 installation is about 200-300 Mb but this is expected to increase significantly as we add media.
Recommended: A locally installed copy (the game itself does NOT have to run) of Civilization III Conquests or Complete edition. Standalone mode is available with placeholder graphics for those who do not have a copy.
- Civilization III Complete is available for a pittance from Steam or GOG

Windows Installation

This is a Windows 64-bit executable. OpenCiv3 will look for a local installation of Civilization III in the Windows registry automatically, or you may use an environment variable to point to the files.

Download and extract the zip file
Double-click OpenCiv3.exe
If it is blocked, you may need to unblock it by
- Right click
- Click on Properties
- Check the “Unblock” checkbox near the bottom buttons in the “Security” section
- Click OK
If your Civilization III installation is not detected, you can set the environment variable CIV3_HOME pointing to it and restart OpenCiv3

Linux Installation

This is an x86-64 Linux executable. You may use an environment variable to point to the files from a Civilization III installation. You can just copy or mount the top-level “Sid Meier’s Civilization III Complete” (Sans “Complete” if your install was from pre-Complete CDs) folder and its contents to your Linux system, or install the game via Steam or GOG.

Download and extract the tgz file
Set the CIV3_HOME environment variable to point to the Civ III files, e.g. export CIV3_HOME="/path/to/civ3"
From that same terminal where you set CIV3_HOME, run OpenCiv3.x86_64
To make this variable permanent, add it to your .profile or equivalent.

Mac Installation

This is a universal 64-bit executable, so it should run on both Intel and M1 Macs. You may use an environment variable to point to the files from a Civilization III installation. You can just copy or mount the top-level “Sid Meier’s Civilization III Complete” (Sans “Complete” if your install was from pre-Complete CDs) folder and its contents to your Mac system, or install the game via Steam or GOG.

Download the zip; it may complain bitterly, and you may have to tell it to keep the download instead of trashing it
Double click the zip file, and a folder including OpenCiv3.app and others will appear
If you try to open OpenCiv3.app it will tell you it’s damaged and try to trash it; it is not damaged
To unblock the downloaded app, from a terminal run xattr -cr /path/to/OpenCiv3.app; you can avoid typing the path out by typing xattr -cr and then dragging the OpenCiv3.app icon onto the terminal window
Set the CIV3_HOME environment variable to point to the Civ III files, e.g. export CIV3_HOME="/path/to/civ3"
From that same terminal where you set CIV3_HOME, run OpenCiv3.app with open /path/to/OpenCiv3.app, or again just type open and drag the OpenCiv3 icon onto the terminal window and press enter
See the wiki for more guidance

Troubleshooting and Known Issues

Compatibility

OpenCiv3 uses many primitive placeholder assets; loading files from a local Civilization III install is recommended (see platform specific setup instructions above)
Support for playing Civ III BIQ or SAV files is incomplete; some files will not load correctly and crashes may occur
Likewise support for OpenCiv3 JSON files (rules and saves) is not yet stable across different versions and they may or may not be reusable.
The Palace view is not yet supported in standalone mode; it opens an invisible overlay that can be closed by pressing Esc.

Game config and logging:

By default OpenCiv3 expects the general config file C7.ini and main log file log.txt to exist in the same directory as the game itself and be writable. It is recommended to install the game to a writable location such as under your user home directory. If the game folder is NOT writable, settings and logs are stored in a per-user Godot data folder instead. Resolved paths and Civ III install detection is now saved in log.txt, so it’s easier to troubleshoot if the game can’t find your Civ III files. See here for more details on user data folder locations.
If you need to set or change the location of Civ III later, or something goes very wrong and the game cannot launch, delete C7.ini and restart the game.
If you encounter a crash, an error dialog for a reason not listed here, or other major problem that you cannot troubleshoot, find log.txt as described above and submit it to us in a GitHub issue or on Discord.

Mac:

Mac will try hard not to let you run this; it will tell you the app is damaged and can’t be opened and ask to move it to Trash. From a terminal you can run xattr -cr /path/to/OpenCiv3.app to enable running it.
See the wiki for more guidance

Other specific bugs will be tracked on the GitHub issues page.

© OpenCiv3 contributors. OpenCiv3 is free and open source software released under the MIT License.