Bell passed up $14.5 million in 2018 by electing not to sign his franchise tag. It was the second straight year he received the tag from the Steelers, preventing him from hitting the open market.
Steelers general manager Kevin Colbert confirmed in a statement that Bell didn't sign the tender.
The 26-year-old will now prepare for his long-awaited free agency, where he'll be the top available running back - if not player.
In five seasons with the Steelers, Bell was selected to three Pro Bowls and named to the All-Pro team twice. He finished three of the past four seasons ranked among the top five in rushing, while also providing plenty of value in the passing game.
The Steelers have hardly suffered without Bell, as second-year tailback James Conner has thrived in an every-down role this season.