The former Manchester United and England midfielder has taken his first managerial role, signing a one-and-a-half-year contract with the team he supported as a boy.
The 44 year old was cleared by the English Football League to take the role, despite holding a 10% stake in Salford City.
The National League side have confirmed he has resigned as a director, but will retain his shareholding.
"Although Paul was never operational in Salford City he will resign as a director of the football club, allowing him to focus completely on his new role at Oldham," Salford said in a statement.
"From the start we have always said that each of the 'Class of 92' would offer different levels of commitment dependant on their individual roles."