Raiders owner Mark Davis announced the decision Friday, per John Dickinson of 957 The Game:
Del Rio signed a four-year deal when he accepted the Raiders job in January 2015, per Jason La Canfora of CBS Sports, and he's exceeded expectations since arriving in the Bay Area.
The Raiders finished one win shy of .500 in 2015; their 7-9 finish gave them as many victories as the franchise compiled during the 2013 and 2014 campaigns combined.
Oakland used that year as a springboard, and the result was a 2016 season filled with prosperity.
Although their season ended prematurely in the postseason after quarterback Derek Carr suffered a broken fibula in Week 16, the Raiders looked like legitimate AFC title contenders when he was healthy.
The defense lagged behind and allowed a 26th-ranked average of 375.1 yards per game, but if that unit can progress toward the league average as the offense continues to evolve under Carr's watch, Del Rio should have the Raiders back in the Super Bowl conversation again next season.