The Storyteller System is the basic set of game mechanics in the role-playing games published by White Wolf Game Studio. Games using this set of rules include the World of Darkness product line, Exalted, the Trinity line, and .

The basic system of resolving conflicts involves the use of ten-sided dice, usually three to ten dice, though Exalted is notable (or infamous) for requiring upwards of twenty or thirty dice to be rolled at a time.

The number of dice to roll is determined by some factor, usually a combination of Attribute plus Ability, based on the player character's statistics. For example, a "Dexterity + Melee" roll for a character with a Dexterity score of 4 and a Melee score of 3 involves 7 dice.

In the old World of Darkness game-line, the Storyteller dictates a "difficulty"; this is the number a player wishes to roll at or above on his dice. The Exalted system uses a flat target number of 7 for almost all rolls, and the Trinity system uses a fixed target number of 6. The the new World of darkness uses a fixed target number of 8, with the exception of a "chance die" rolled if the player has no dice normally, which has a target number of 10.

The player then rolls his allotted number of dice, counting the number of dice that came up at or above his target number. This total is the number of "successes" achieved for the action the player rolled for. For example, a roll of five dice with 7, 7, 3, 2, and 10 would be a total of 3 successes, assuming a target number of 7.

The old World of Darkness games offered a "specialty" rule, where a result of 10 on any die allowed an extra die to be rolled when the roll pertained to some specialty the character had trained in or was adept at. In the new games, each 10 rolled allows another die to be rolled at a target number of 10, and in some cases this can be changed to a 9. In Exalted, 10s automatically count as two successes for non-mortal characters (for example, Exalted, spirits, Fair Folk, and other magical beings).

In the old World of Darkness games, each 1 rolled subtracts an effective success. In Exalted, 1s do not count unless the player also rolled no successes. In either case, the result is a "botch", or a spectacularly bad failure at the task being attempted (for example, a player who botched a roll to jump off a train might break a leg). In the new World of darkness games, if the player has no dice to roll normally, a single die is rolled to a target number of 10 and only on this roll can a 1 count as a botch (or, as these games call it, "dramatic failure")

Ordinarily, only a single success is required to achieve the player's goal. In many cases, particularly trying or challenging tasks are assigned a threshold, a minimum number of successes needed to succeed. For example, convincing a suspicious guard of your good intentions may be a "threshold 3" roll; it is made harder because of the guard's wary nature, and the player must roll at least 3 successes to succeed at all. In Exalted, the term is "difficulty", and the roll required (7 or above) is called the "target number". This difference can sometimes be confusing for players moving from one system to the other, because of the use of "difficulty" in the World of Darkness rules.

More complicated variations on this basic idea are introduced in each game-book's rules, such as opposed rolls (where two or more characters roll to achieve more successes than the others).

See also d20 System.