Stunning Spell

"The jet of red light hit the Death Eater in the middle of his chest: he froze, his arm still raised, his wand fell to the floor with a clatter and he collapsed backwards towards the bell jar."

- Description.

The Stunning Spell (Stupefy), also known as a Stunner or Stupefying Charm 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. If the spell is used by multiple wizards aiming at the same target, the damage it causes is increased, 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 expressed surprise that it did not kill her. Dragons are able to shrug off a single Stunning Spell, but if multiple Stunning Spells are aimed at a dragon, they will work. It manifests itself as a jet of scarlet light.

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 English stupefy, which means "to stun" or "to amaze". It may also come from the Latin stupere, meaning "to be stunned".

Behind the scenes

 * Another variation of the spell is Stupefy Duo.
 * In the books, it is described as a "jet of red light," and appears as such at the beginning of the film adaptation of Harry Potter and the Goblet of Fire, when Ministry of Magic Officials apparate near the trio and attempt to stun them after the destruction of the Quidditch World Cup fair grounds. However, from the film adaptation of Harry Potter and the Order of the Phoenix on, it is shown as blue light that often just knocks people off their feet.
 * Harry counters unidentified green curses cast by Death Eaters with the Stunning Spell, causing the spells to collide and explode in midair. If these green curses were Killing Curses, then this would indicate that Killing Curse can be parried if it collides with another spell.
 * In the video game adaptation of Harry Potter and the Half-Blood Prince, Stupefy is shown as a ball of red light, but when cast by opponents, it is green, like the Killing Curse.
 * 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 LEGO Harry Potter: Years 1-4, it can be bought at Wiseacre's Wizarding Equipment in Diagon Alley.
 * Flavius Belby tried to use this spell against a lethifold, however it had no effect as lethifolds can only be repelled by the Patronus Charm.
 * In Harry Potter and the Deathly Hallows: Part 2, Hermione casts Stupefy at Blaise in the Room of Requirement instead of Gregory Goyle. This is due to Crabbe's part being replaced by Blaise and thus is Goyle is the one to conjure the Fiendfyre.
 * It has been implied that Dobby does this to Wormtail in Harry Potter and the Deathly Hallows: Part 1. However, when Harry does this to Umbridge and Mafalda, they are instantly knocked out, while Wormtail stands for a few seconds, says "Ow" (hinting that the spell was quite painful) and collapses. This, as well as his unintended non-reappearance in Part 2, suggests that he may be dead, or that Dobby used a different spell to knock him out.
 * In Deathly Hallows: Part 2, Voldemort casts Stupefy at Neville Longbottom out of anger, after Harry Potter seemingly came back to life. Neville was blown backward into the Great Hall, and remained unconscious until he woke to slay Nagini.
 * In Harry Potter and the Order of the Phoenix during one of the classes of the DA, Harry calls a Stunning spell "a wizard's bread and butter."
 * In Harry Potter for Kinect Harry and Voldemort can use this spell against each other in the final battle during Voldemort's Last Stand as they engage in a normal duel.

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
 * LEGO Harry Potter: Years 5-7
 * Harry Potter: Spells
 * Harry Potter and the Deathly Hallows: Motorbike Escape
 * Harry Potter Trading Card Game
 * Wonderbook: Book of Spells
 * Wonderbook: Book of Potions
 * Harry Potter for Kinect
 * Pottermore

Notes and references
Hechizo Aturdidor Sortilège de Stupéfixion Tainnutu Schiantesimo