0 A.D. is a free and open source real time strategy (RTS) game that has similarities to Microsoft's Age of Empires series. 0 A.D. has your typical RTS components such as: building up your base, training your army, researching technology, upgrading your units and buildings and waging war against your enemy. The game has a wide selection of ancient civilizations to play like: The Romans, Carthaginians, Persians, Celts and more.
Mac OS X 10.4 or newer
Intel powered Mac 1.0 GHz or faster
512 MB RAM
Free download at wildfiregames.com