We all knew this day would come: The zombie apocalypse "World War Z" trailer has finally arrived.

Starring Brad Pitt and "The Killing" star Mireille Enos — and adapted from the novel by Max Brooks — "World War Z" is a nightmarish tale of the whole planet overrun by undead. The first trailer shows order unravelling around Gerry Lane (Pitt), a United Nations employee who travels the globe trying to stanch the flow of a zombie pandemic. 

And what a zombie pandemic it is. These are no shambling Romero creatures; they're not even the fast-moving but independently operating monsters of "28 Days Later." The zombies of "World War Z" are like a wriggling, biting wave of destruction, climbing up walls and over each other to reach their prey.

It's basically the most terrifying thing we've ever seen. Here, have some nightmares: