Warhammer: Mark of Chaos is a real-time tactics game set in the Warhammer universe. It was developed by Black Hole Entertainment and co-published by Namco Bandai Games in North America and Deep Silver in PAL territories in November 2006.

An expansion, Battle March, was released in September 2008. It contains one new campaign and the addition of Dark Elves and Orcs & Goblins as playable races. An Xbox 360 version was released and titled as Warhammer: Battle March, dropping the Mark of Chaos moniker.

The game, according to the developers, is a game "focusing on the armies and battles while de-emphasizing the tedious aspects of base and resource management". Set in the Warhammer Old World, the player can command one of four armies from the tabletop game.

The gameplay is primarily focused on battlefield tactics, thus not featuring RTS gameplay aspects like base-building, resource harvesting or in-battle unit production. Instead, the gameplay is intended to be focused on high fantasy/late medieval battles. Its gameplay is superficially similar to its predecessors and the Total War games; however, the basic game play model is significantly more simplified, and battles are more similar to real-time strategy games like Warcraft III than other real-time tactics titles.

The objective for each battle is defeat of the enemy army by either completely destroying it or causing the remaining units to flee off the battlefield. Battles are fought on a variety of landscapes and settings, with specific terrain types granting bonuses or penalties to units. Units also have morale, and will break and flee if they suffer enough damage or get hit by specific types of weaponry, and stamina, which will cause them to lose defense and speed when sufficiently drained.

The troops present in the game are presented as "units", which is anything from 1 to 96 individual "models", with the specific number depending on the type of unit. The control system is similar to the Total War and Dawn of War in that orders are issued to units in their entirety, as opposed to being issued to individuals. As well as standard orders you are also able to arrange your units into a number of formations, with each formation conferring advantages against specific kinds of attacks. Units will also gain experience over the course of a battle or campaign and will gain improved statistics and more models.

In addition to standard units there are special "Hero" units; unique individuals considerably more powerful than the average combatant. In addition to being able to use and learn new abilities, they can also be equipped with additional weapons, armour or potions that grant the hero with both offensive and defensive skills and bonuses. Heroes also gain experience from fighting, and by gaining levels the player is able to unlock various skills that supplement its combat abilities. Unlike units which consist of multiple models, Heroes are controlled individually. However they can be attached to standard units, fighting alongside the unit's models, giving the unit a morale boost and increasing its fighting capability through the use of skills. Hero units can also initiate or be challenged to duels, where they fight the opposing army's hero uninterrupted until one slays the other, resulting in a morale penalty for the losing side. The duel is for the most part out of the player's control, however the player is also free to activate any duel-specific skills the hero has during the course of the duel, to affect its outcome.

There are two single player campaigns, each separated into four chapters, one following the Empire and Elven Forces and the other the Hordes of Chaos and Skaven forces.