A Freeform Magic system is a game mechanic that does not use a fixed system of spells to represent the use of magic in its world. Most games using magic have some form of list of spells or powers which the player chooses from, each having a fixed set of effects. In a freeform system there is instead a method by which the players/characters may create their own spells. These systems are an attempt to more comfortably portray the kind of magic that appears in many mysterious fantasy novesl, such as The Weirdstone of Brisengamen. (Alan Garner) Although such a system is much harder to use in play, it does allow a much wider variety of effects in the game.

The major drawback with a Freeform Magic system, in many people's oppinion, is that it does not have the strangeness and interest of a spell based system. Many games have spells which are essentialy the same in effect but are made different by their descriptions. A Lightning bolt, fireball, or summoned Demon-spirit may in fact cause the same ammount of damage, but they are made to seem widely different from their descriptions. A spell conjuring spirit snakes to swarm over and strangle a foe would, in a Freeform system, probably end up as a formless and undefined damage spell no different from any other damage spell.

Another problem is that Freeform Magic systems are difficult to run during a game. When the effects of a spell are clearly defined in the rules it is easy to quickly cast the spell and adjudicate the outcome. If the players must stop, construct the spell, and then decide exactly what its effects are, everytime they want to use magic, then it slows down the progress of the game significantly. Indeed though a freeform system is supposed to free up the use of magic and make it simple and easy, they usually entail an incredible number of rules which attempt to make the system usable, more riules, in fact, than a non-freeform system might use.

Significant systems employing freeform magic include Ars Magica, Mage and Amber.