The fourth season of Supernatural, an American dark fantasy television series created by Eric Kripke, premiered September 18, 2008, and concluded on May 14, 2009, on The CW.

The angels intervene to rescue Dean from Hell and bring him back to life after he became trapped there in the third season finale "No Rest for the Wicked".

While Kripke originally did not want angels to be featured in the series,[23] he changed his mind when he realized that he needed them in order to have a "cosmic battle" with the many demons.

[24] With this concept added into the series' mythology, the writers came to view the show as being "about two greasers and a muscle car, but the canvas that they're on are demons and angels and battles and the apocalypse..."[24] While it was originally intended for the fourth season to feature an "all-out demon war", budget cuts forced the writers to change their plans, making it "smaller, more contained, underground, more guerrilla-style".

Kripke feels this ended up benefiting the series, believing the brothers-centric episodes to be more interesting than the "epic" ones of the third season.