The fourth season of The Hills, an American reality television series, consists of 20 episodes and was broadcast on MTV. It aired from August 18, 2008, until December 22, 2008. The season was filmed primarily in Los Angeles, California, with additional footage in New York City, New York; Las Vegas, Nevada; Italy; and Cabo San Lucas, Mexico. The executive producer was Liz Gateley.

The Hills focuses on the lives of Lauren Conrad, Audrina Patridge, Whitney Port, and Heidi Montag. During the season, Conrad's distaste for Montag's boyfriend Spencer Pratt continues to inhibit reconciliation between the women. Meanwhile, Patridge is concerned that her new housemate Lo Bosworth is straining her relationship with Conrad. The season finale saw Port relocate to New York City to accept employment with Diane von Fürstenberg, while Montag and Pratt elope.

Upon the conclusion of the season, Port was commissioned her own spin-off series The City, which originally chronicled the lives of her and friends Olivia Palermo, Jay Lyon, Erin Lucas, and Adam Senn. Additionally, rumors were widespread that Conrad wished to leave the series to pursue other career opportunities, though she made her final appearance on the series during the mid-season finale of the following season.