The Stunning Spell (sometimes referred to as a Stunner) was a spell used to knock a target unconscious. It could also be used to stop moving objects, and its counter-spell was the Reviving Spell. Stupefy Duo was the more powerful version of this charm.

Very useful in duelling, this spell can be deflected by a Shield Charm, and also wears off with time. It can also be 'stacked' by multiple people casting it, which can be useful against creatures that are resistant to most spells, like dragons, giants, or trolls, but will cause injury to normal witches or wizards.