The Washington Redskins said Tuesday that Portis and owner Dan Snyder will hold a retirement news conference Thursday.
Portis played two seasons with the Denver Broncos and then seven with the Redskins. He is most remembered for the colorful array of characters he created each week during the team's drive to the playoffs in 2005. His 1,516 yards rushing that season set a franchise record.
The Redskins cut Portis after a torn groin muscle ruined his 2010 season, unwilling to pay for another year of his expensive contract.
He was unable to find another team and ends his career 77 yards shy of 10,000, No. 27 on the NFL's all-time list.