General manager Tom Telesco announced the news at a press conference, per Josh Alper of Pro Football Talk.
Warren Sharp broke down the history of fifth-year options for running backs:
The Chargers selected Gordon with the No. 15 overall pick out of Wisconsin in 2015, and he signed a four-year deal worth more than $10.6 million with an option available for the 2019 campaign, per Spotrac.
Gordon was a force in college with 2,587 rushing yards in his final season for the Badgers, so there were plenty of expectations surrounding him as a first-round pick. However, he didn't meet them right away and struggled to hit holes at the NFL level and serve as the game-changer he was in college.
He tallied 641 rushing yards on 3.5 yards per carry and zero touchdowns as a rookie, but he turned the corner the following two seasons as he became more of a two-way threat as a pass-catcher out of the backfield.
Gordon finished with 997 rushing yards, 419 receiving yards and 12 total touchdowns in 2016 before posting 1,105 rushing yards, 476 receiving yards and 12 total touchdowns in 2017.
There is plenty of reason for optimism moving forward as well considering he is just 25 years old.
"The way he finished the season, I'm very comfortable (with Gordon)," head coach Anthony Lynn said of the running back, per Dan Woike of the San Diego Union-Tribune. "I thought he was one of the best runners in the game the last four weeks. It just seems like the bigger the game, the better he plays."
Gordon will have the chance to continue playing well in bigger games for the Chargers after they decided to keep him aboard for a fifth season.