The 1925–26Ottawa Senators season was the club's 41st season of play and ninth season in the NHL. The Senators placed first during the regular season but were upset in the playoffs by the Montreal Maroons.
The Senators welcomed the Stanley Cup champion Victoria Cougars to town for two exhibition games on November 19 and 21, with proceeds to the Ottawa Humane Society. Ottawa won both games, 6–2 and 2–0.
Ottawa, who missed the playoffs the previous season, would go on to finish with a league best 24–8–4 record, and earn a bye in the first round of the playoffs, however, they were upset by the Montreal Maroons in the NHL final, losing the two-game total-goal series 2–1. Cy Denneny would once again lead the club offensively, scoring 24 goals and 36 points, while Frank Nighbor would win the Lady Byng Trophy for the 2nd straight season.
The Senators went against the Maroons in a two-game total-goals series for the NHL championship and lost two goals to one. The Maroons had Punch Broadbent and goaltender Clint Benedict, two former Senators stars in the lineup, who would figure prominently in the series.
By placing first, the Senators had a bye to the NHL Championship round against the second-place Maroons who had defeated the Pittsburgh Pirates. At home in the first game, the Maroons tied the Senators 1–1. Former Senator Punch Broadbent scored at 8 minutes of the second period to put the Maroons ahead. The lead lasted until King Clancy tied the game with ten seconds left. In the second game, held at Ottawa, the Maroons took the series with a 1–0 shutout victory to win the NHL championship. Babe Siebert on an individual rush, scored off his own rebound at the six-minute mark of the second period. Cy Denneny appeared to tie the score a minute later, but the play was off-side. The Maroons held off the attack of the Senators the rest of the way in front of a record attendance of 10,525.
After the playoff, the Senators welcomed the Saskatoon Sheiks for a pair of exhibition games on April 1 and April 3. The series matched the two leagues' runner-up teams. The Senators won the first game, played under NHL rules 4–3. The second game was played under WHL rules and the Sheiks won 7–5. The Sheiks were on an exhibition tour and played in Montreal on April 4 against the Canadiens in a benefit game for Georges Vezina's family.