Defence of the Ancients (called DOTA for short) is a custom game map created for the game Warcraft 3. Originally developed for Warcraft 3 :
Reign of Chaos (and wildly popular) by
Eul, the map was later ported onto Frozen Throne (the expansion pack for Warcraft 3), was released. Currently the most popular ports of DOTA are Allstars, CHAOS and Classic.