From Diablo Wiki
Stun is an ability to daze one or many nearby enemies in place rendering them immobile and unable to attack for a short time.
The Barbarian class in Diablo III has a few stun abilities and passives that can be tweaked through the skill trees.
The Wizard in Diablo III has a few stun abilities that may stun enemies.
Charged Bolt is a Tier 1 active skill that causes critical hits from lightning damage to stun targets for 2 sec. This ability is found in the [Storm Skill Tree].
Thunderstruck is a Tier 1 passive skill that increases the critical hit chance of all lightning spells by X%. This means the chances to stun targets for 2 seconds increases when you apply extra points to this skill. Thunderstruck may be found in the [Storm Skill Tree].
Electrocute is a Tier 3 active skill that benefits from critical strikes and Thunderstruck to cause enemies to be stunned for 2 sec.
Improved Charged Bolt
Improved Charged Bolt is a Tier 3 passive skill that increases the number of bolts released by your charged bolt spell. At this tier, with a good amount of points in Thunderstruck (increases critical strike on lightning attacks) the stun chance is increased. Good against multiple enemies.