Lee Erwin goal earns 10-man Oldham a vital victory
Sheffield United were confirmed as Sky Bet League One champions after nearest challengers Bolton suffered a 1-0 defeat at 10-man Oldham.
Wanderers' own promotion bid is faltering after back-to-back losses, though they still hold a four-point lead over third-placed Fleetwood.
The home side created the first chance as Lee Erwin beat two defenders before pulling his shot a yard off target.
Darren Pratley twice fired over for Bolton in a dour opening half which was dominated by well-drilled defences.
Oldham almost scored when visiting goalkeeper Mark Howard palmed out Peter Clarke's shot before also saving from Paul Green, but they went down to 10 men in the 64th minute as striker Michael Ngoo picked up his second yellow card for a foul on Dean Moxey.
The Latics still broke through after 76 minutes when Howard parried a low cross against team-mate Jay Spearing and Erwin claimed his 10th goal of the season by helping the ball over the line.
Bolton were denied when Dorian Dervite's effort was cleared off the line by Ryan McLaughlin, while Adam Le Fondre and Chris Long both hit the crossbar in a frantic finish.
Oldham's win saw them move six points above the relegation zone.