Alastor "Mad Eye" Moody is a fictional character in the Harry Potter series of books, an ex-Auror working for the Order of the Phoenix.

As an experienced Auror, who has lost an eye, leg, and part of his nose while fighting the Dark Arts, Moody is cautious—some might say paranoid—and refuses to eat or drink anything which he himself has not prepared. He is particularly conspicuous because of his peculiar magical eye which can see through walls, doors, and the back of his own head (hence the nickname "Mad Eye").

Brendan Gleeson will play Moody on screen in Harry Potter and the Goblet of Fire. "Moody" means "temperamental" or "sulky."

In Harry Potter and the Goblet of Fire, Moody was appointed as the Defence Against the Dark Arts teacher at Hogwarts. Before the school year began, however, he was locked up in a chest by Barty Crouch Jr, a follower of Voldemort, who used a Polyjuice Potion to take his form in order to replace him. Moody owes his life to the fact that one ingredient of the Polyjuice Potion is a part of the person whose form is to be assumed, such as a tuft of hair. Moody's habit of carrying his own drink allowed Crouch to take the Potion regularly without raising suspicion.

On the night of the final task, Crouch attempted to kill Harry, but was stopped by Albus Dumbledore and Minerva McGonagall. Having neglected to take his hourly dose of potion, Crouch returned to his own appearance and, under the influence of Veritaserum, he admitted everything.

Harry first meets the genuine Moody just prior to his fifth year at Hogwarts, in Harry Potter and the Order of the Phoenix. In that book, Moody has joined the newly reformed Order of the Phoenix, and is usually accompanied by fellow Order members Nymphadora Tonks and Remus Lupin, especially while protecting Harry.