The 1998–99 OPJHL season is the sixth season of the Ontario Provincial Junior A Hockey League (OPJHL).
The thirty-seven teams of the Central, East, and West divisions competed in a 51-game schedule.
The top eight of each division made the Buckland Cup playoffs.
[1] Note: GP = Games played; W = Wins; L = Losses; OTL = Overtime losses; SL = Shootout losses; GF = Goals for; GA = Goals against; PTS = Points; x = clinched playoff berth; y = clinched division title; z = clinched conference title Division Quarter-final Division Semi-final Division Final Semi-final (*) denotes that the Merchants were welcomed back into the playoffs for another round despite losing due to their superior playoff winning percentage over Couchiching and Lindsay.
Round Robin Semi-final Note: GP = Games played; G = Goals; A = Assists; Pts = Points; PIM = Penalty minutes