Scholes has resigned from his role as director of Salford City although he retains his 10 per cent share in the club.
Former Oldham coach Mick Priest will be Scholes' assistant as he embarks upon his first managerial role.
"Paul has won everything there is to win in football," Oldham owner Abdallah Lemsagam said.
"He is a man who will bring a lot of footballing knowledge and his hunger to succeed in management will be there for everyone to see.
"It's no secret how much he has wanted this job in the past and how much he loves this club, so I'm very happy to bring him into our family at Oldham Athletic.
"Paul will have my backing 100 per cent and hopefully we can work together to bring success back to this club.
An EFL board meeting decided last week there was not a conflict of interests because of Scholes' 10 per cent stake in Salford City who, despite playing in the National League, are fighting for promotion to League Two.
The only restriction to Scholes is he will not be allowed to sign players from, or sell to, Salford City.
