The 44-year-old signed a one-and-a-half year contract with the League Two side.
At Boundary Park, Scholes will lean on his coaching experience at United, a brief caretaker stint at Salford City, and the expertise of Mick Priest, who's joining Oldham as an assistant after previously coaching at the club.
"Paul has won everything there is to win in football," club 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 percent and hopefully we can work together to bring success back to this club."
Scholes' familiarity with Oldham - he's been a vocal supporter of the club throughout his time in football - and his work with non-league Salford should reduce the risk of a culture shock for the former midfielder. By the time he hung up his boots for the second time in 2013, Scholes had made 718 appearances for Manchester United and collected 11 Premier League titles, two Champions League trophies, five domestic cups, and plenty of other silverware in that time.
The Latics, on the other hand, are 14th in the fourth tier of English football and have lost to nearby rivals Rochdale and Macclesfield Town this season. Their greatest successes were overseen by Joe Royle, who led Oldham to the 1990 League Cup final, two FA Cup semifinals, and incredibly kept the Greater Manchester outfit in the top flight for three seasons following promotion in 1992.
With Scholes now in charge, Oldham will play three consecutive home matches against Yeovil Town, Crewe Alexandra, and Morecambe before a local derby at Bury on Feb. 23.