The 2003–04 OPJHL season is the 11th season of the Ontario Provincial Junior A Hockey League (OPJHL). The thirty-five teams of the North, South, East, and West divisions competed in a 49-game schedule. Come February, the top eight teams of each division competed for the Frank L. Buckland Trophy, the OPJHL championship. The winner of the Buckland Cup, the Aurora Tigers, went on to win both the Dudley Hewitt Cup as Central Canadian Champions and the 2004 Royal Bank Cup as National Champions.