In the Warhammer 40,000 fictional universe, a Titan is a colossal, and usually humanoid, mecha.
Titans are considered the largest and most powerful types of War Engines and primarily feature in the Epic series of games. War engines vary immensely in role and size, ranging from battle titans to super-heavy tanks and large transports; the only thing that they have in common is that they can suffer repeated successful hits that would otherwise destroy smaller vehicles and units. In the current version of the Epic game, War Engine damage capacity is represented by hitpoints, of which Titans have the most.
In the game of Epic, the smallest Titan model stood around 7 cm high next to a standard human at around 6 mm. In Warhammer 40,000, the smallest of the Imperial Titans, the Warhound, also towers over the human sized 28mm tall models at some 10.5 inches. In the Winter Assault expansion to the computer game Warhammer 40,000: Dawn of War, the head of an Imperator Titan, the largest of the Imperial titans, alone is at least 12 metres tall. Both Dawn of War and Epic stay more true to the backstory than the Warhammer 40,000, as Monstrous creatures, such as the Bloodthirster, Avatar of Khaine and Daemon Princes are much larger as compared to human sized models than their Warhammer 40,000 counterparts.