And he has dropped down two divisions to play for Darlington, where he will be reunited with Dave Penney.
Penney managed Foster at Doncaster, but after a row the player was allowed to move to Scunthorpe on a free transfer last season.
"It has been no secret that one of my main priorities was to strengthen the back four," said Darlo boss Dave Penney.
"Stephen knows what it takes to achieve promotion having been voted Scunthorpe's player of the season."
Foster made a total of 68 appearances in his year-and-a-half as an Iron player.