I Am Number Four is a young adult science fiction novel by Pittacus Lore (the pseudonym of James Frey and Jobie Hughes) and the first book in the Lorien Legacies series.

The book was published by HarperCollins on August 3, 2010, and spent seven successive weeks at #1 on the children's chapter of the New York Times bestseller list.

[3] The first book of the "Lorian Legacies Series", "I am Number Four" centers on the conflict between two extraterrestrial species: the Loric and the Mogadorians.

The Loric are classified into two factions: the overseers known as the Cepân and the guardians known as the Garde, the latter of whom possess unique abilities known as Legacies.

The story begins with a prelude that follows Hannu – the alias used by Number Three, one of nine Garde children who fled to Earth after their homeworld of Lorien was invaded.

As the story opens, he and his guardian or Cepân, Henri, learn of the death of Number Three and move to Paradise, Ohio, assuming a new identity as John Smith.

There, John befriends conspiracy theorist Sam Goode and "adopts" a dog identified by its name tag as "Bernie Kosar".

During a Halloween parade, Sam mentions that he knows about Mogadorians from a magazine, They Walk Among Us, a revelation that alarms both John and Henri.

At a party at Mark's house, a major fire breaks out, trapping Sarah and forcing John to use his powers to save her.

A furious battle ensues, during which Six exhibits powers of invisibility and control of the weather, and Bernie Kosar is revealed to be a Chimæra, animals on Lorien who can shape shift.

Kirkus Reviews wrote, "If it were a Golden Age comic, this tale of ridiculous science, space dogs and humanoid aliens with flashlights in their hands might not be bad.

"[7] School Library Journal wrote, "With its interesting premises and a fast-pace telling, the story will grab readers who are willing to suspend quite a bit of disbelief.