Confundus Charm

"Unnoticed by Travers, who was looking through the bronze doors at the inner hall, each of the guards gave a little start as the spells hit them. The guard was confused. He stared down at the thin, golden Probe and then at his companion, who said in a slightly dazed voice, 'Yeah, you've just checked them, Marius.'"

- The Gringotts guards, confused by a Confundus Charm placed on them by Harry Potter

The Confundus Charm (Confundo ) is a charm which causes confusion in a person or bewitch an object. It appears that there are varying degrees of confusion caused by the spell, from simply tricking a person or thing about a specific incident to confusing a person to the point at which they endanger themselves.

Practitioners

 * Barty Crouch Jr.
 * Hermione Granger
 * Ronald Weasley
 * Severus Snape
 * Harry Potter

Casting
The spell seems to be rather difficult to cast, as Severus Snape, an exceptionally powerful wizard who could flawlessly perform Nonverbal spellcasting and Wandless spells, had such trouble with it that he had to "frown in concentration". To cast it, one must point their wand directly at the person or thing that must be confused and incant, "Confundo". If one is casting the charm on multiple targets, they must point their wand at each individual target in turn and incant once for every individual target.

Effects
Although the spell carries no light or sound, one can detect if another person has been Confunded (someone who has had this spell cast on them has been "Confunded") only immediately after the spell has been cast; the person will shudder when the spell hits them. It will cause any of varying degrees of confusion, from a simple trick to making a person believe that they have come up with a complex plan when said plan was given to them by the caster. It can also be used on inanimate objects that have a level of sentience, as Barty Crouch Jr. did with the Goblet of Fire, though this was noted to be a difficult task, as the Goblet itself was a powerful magical artefact.

Etymology
Confundus, as well as the incantation Confundo, are derived from the Latin verb confundo (confundo-confudi-confusum-confundere), meaning "to confuse, to perplex."

Behind the scenes

 * In the films and video games, the incantation for this charm is Confundus, and not Confundo as it should be.
 * Professor Severus Snape repeatedly insisted that Sirius Black had cursed Harry Potter and Hermione Granger with this spell; however, this was false, as Black was actually telling the truth.

Appearances

 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Goblet of Fire (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1 (video game)
 * LEGO Harry Potter: Years 5-7
 * Harry Potter: Spells
 * Harry Potter Trading Card Game
 * Pottermore

Notes and references
Sortilège de Confusion Incantesimo Confundus Конфундус