The 1914–15 Ottawa Senators season was the Ottawa Hockey Club's 30th season of play since its founding in 1883 (with some inactive years in the 1880s). After placing fourth in 1913–14, the Senators improved to win the NHA title, but lost the inaugural Stanley Cup 'World Series' playoff to the Vancouver Millionaires, played in Vancouver.
The 1914–15 season was the first year of an agreement by the Cup's trustees, the NHA and the PCHA where the champion of each league would compete for the Stanley Cup. It marked the end of the challenge era, and began a twelve year period where the NHA/NHL champion would have to compete against a Western league for the Cup.
All three games in this series were played in Vancouver, British Columbia, with the Millionaires sweeping the best of five series in three games.