The Chargers (11-3) edged Cincinnati 27-24 on Sunday, and when Denver lost to Oakland, the AFC West belonged to San Diego for the fourth straight season.
"It's an incredible feeling," star outside linebacker Shawne Merriman said.
"It's all kind of a blur," added Nate Kaeding, whose 52-yard field goal won it. He hadn't gotten a division championship cap until team president Dean Spanos walked by in the locker room and gave the kicker his.
The Cardinals (9-5) won the NFC West for the second successive year by beating Detroit 31-24, then having San Francisco lose at Philadelphia 27-13. The Eagles (10-4) moved into the postseason with that win.
"We're not happy with how we played," Larry Fitzgerald said. "We know we need to improve, but the opportunity to win double digits, I don't know the last time a Cardinals team was able to do that."
That would be 1976 when they represented St. Louis.
Philadelphia made the playoffs for the eighth time this decade.
"It's always good to clinch a spot early, but we're still going to put our foot on the pedal," Donovan McNabb said. "It's an exciting time, but nothing to get overly excited about. One of our goals is to have a bye week and win the NFC East and the only chance for that to happen is to win the last two games."
Philly hosts Denver, then travels to Dallas, which is one game behind the Eagles in the division.
Green Bay's 37-36 defeat at Pittsburgh gave the Vikings (11-2 and playing at Carolina on Sunday night) the NFC North.
Indianapolis already clinched the AFC South and New Orleans owns the NFC South.