The 1903 Canadian Amateur Hockey League (CAHL) season was the fifth season of the league. Teams played an eight game schedule. Ottawa and Montreal Victorias tied for the league championship with records of six wins and two losses. Ottawa defeated the Victorias in a two-game playoff to win the season and their first Stanley Cup championship, the first of "Silver Seven" era.
It was decided that league champions would not play for the Stanley Cup until after the season. If a challenge was ordered by the Cup trustees, Montreal would default the Cup. A challenge was ordered by the trustees and Montreal eventually agreed to play Winnipeg in January during regular season play.
This season saw the loss of several players to hockey leagues in the U.S., including Charlie Liffiton, Hod Stuart, Bruce Stuart, Eddie Hogan and George McCarron.