Stunning Spell

The Stunning Spell is a charm that renders a victim unconscious and halts moving objects. It is commonly used in duels, and was one of the spells Harry Potter taught Dumbledore's Army. The spell gains strength when many wizards cast it on the same target; for example, Professor McGonagall had to be moved to St Mungo's after being hit with the spell by multiple Ministry of Magic employees in 1996, and Madam Pomfrey commented that it was a surprise that she did not die. The incantation for this spell is Stupefy.

The effects of the spell seem somewhat inconsistent, with those hit by it variably being knocked unconscious, knocked down, freezing in place, or being sent flying backwards through the air. This could depend on the skill and intent of the caster.

Defence against the Stunning Spell
The effects of a Stunning Spell may be counteracted by Rennervate, but will also wear off with time. It can also be deflected by a Shield Charm. Species known to be naturally resistant to the spell include dragons, trolls, giants and half-giants. Rubeus Hagrid was unaffected by this spell when, in 1996, several Ministry of Magic employees attempted to remove him from Hogwarts grounds.

It is also possible to bewitch objects to be resistant to the spell. Fred and George Weasley bewitched their fireworks to explode when hit by Stunning Spells.

Etymology
"Stupefy" comes from the Latin verb stupere, meaning "to be stunned."

Behind the scenes

 * In the books, it is described as a "jet of red light," but in the film version of Harry Potter and the Order of the Phoenix, it is shown with a bluish-white that just knocks people off their feet.
 * In the video game adaptation of Harry Potter and the Half-Blood Prince, Stupefy is shown as a jet of red light, but when cast by opponents, it is green, like the Killing Curse, Avada Kedavra.
 * In Harry Potter and the Deathly Hallows, Hermione attempts to use a Stunning Spell on one of the enemy giants, but is prevented from doing so by Ron as it would "crush half the castle." However, it was Hermione herself who pointed out in Harry Potter and the Order of the Phoenix that Stunning Spells are almost completely ineffective against Giants, even when cast by multiple wizards.
 * In Harry Potter and the Deathly Hallows: Part I (video game), the Stunning Spell is blue.
 * In Lego Harry Potter: Years 1-4, it can be bought at Wiseacre's Wizarding Equipment in Diagon Alley.

Appearances

 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1
 * Harry Potter and the Deathly Hallows: Part 1 (video game)
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)
 * Lego Harry Potter: Years 1-4
 * Harry Potter: Spells
 * Harry Potter and the Deathly Hallows: Motorbike Escape 

Notes and references
Sortilège de Stupéfixion Tainnutu