The 1942–43 NHL season was the 26th season of the National Hockey League (NHL). The Brooklyn Americans were dropped, leaving six teams to play a schedule of 50 games. This is the first season of the "Original Six" era of the NHL. The league's long-time president Frank Calder died due to heart disease. The Detroit Red Wings defeated the Boston Bruins to win the Stanley Cup.

The Brooklyn Americans franchise was dropped, as Madison Square Garden turned down a lease agreement with team owner Red Dutton. Dutton argued that the other teams would be weakened by the war, but the other owners pointed out the number of American players serving in the armed forces was such that the Americans could not operate. A despondent Dutton left the league meeting, but was to return to the NHL sooner than he thought.

With the suspension of the Americans, this was the inaugural season of the so-called Original Six era, with the NHL consisting of six teams (the Boston Bruins, Chicago Black Hawks, Detroit Red Wings, Montreal Canadiens, New York Rangers, and Toronto Maple Leafs). This arrangement would last until the 1966–67 season, after which the league doubled in size.

The league's meeting of January 25, 1943, was to have been a non-event. The only news that was supposed to come out of the meeting was that the playoffs would begin on March 20, and that all series would be best-of-seven affairs. This was resolved in the morning session.

The afternoon session had just begun and NHL president Frank Calder had informed Red Dutton of the reserve status of his suspended franchise, when Toronto coach Hap Day noticed that Calder appeared to be in pain. Two league governors came up to his aid, but he assured them he was all right. Then Calder's face contracted as if he were in pain. He took a few steps and exclaimed "My God, there IS something wrong!" He was taken to his hotel room and a doctor diagnosed a heart attack. A specialist convinced him, despite his protests, to check into St. Michael's Hospital in Toronto, where he suffered a second heart attack. In a week, Calder felt well enough to return to Montreal and checked into Montreal General Hospital. After eating a light breakfast surrounded by his family and friends, he was looking over the league books when he slipped back on the pillows of his bed and died of a third heart attack. He died on February 4, 1943, at the age of 65 years. Red Dutton was chosen as the new president, on an "interim" basis.^[1]

Due to war-time travel restrictions, the NHL ceased playing overtimes to decide tie games on November 21 partway through the season. The last regular season overtime game was November 10, 1942, between the Chicago Black Hawks and the New York Rangers, won by New York 5–3. Regular season overtime would not be re-introduced until the 1983–84 NHL season.

Detroit finished first, partly due to the six shutouts of goaltender Johnny Mowers, who won the Vezina Trophy. During the season, Jimmy Orlando got into a stick-swinging incident with Toronto rookie Gaye Stewart and came out of it on the short end, badly cut in the face and bleeding profusely. Both players were suspended for the incident.

The Montreal Canadiens were still making progress, and coach Dick Irvin put together the first "Punch Line" of Elmer Lach, Toe Blake and Joe Benoit. Maurice Richard showed promise, but broke his leg, and Canadiens' manager Tommy Gorman began to look at him as brittle. Benoit became the first Canadien to hit the 30 goal plateau since Howie Morenz did it in 1929–30 (40 goals) scoring an even 30. Gordie Drillon also added some scoring power. The Canadiens made the playoffs by one slim point and lost to Boston in the playoffs' first round.

In contrast to the 1941–42 season, the Rangers felt the full impact of World War II and lost Art Coulter, Alex Shibicky, the Colville brothers, and Bill Juzda to the Armed Forces. Only Ott Heller was left of their defence. Babe Pratt was traded to Toronto for Hank Goldup and Dudley "Red" Garrett. Garrett proved to be an excellent replacement for Pratt. However, he only played 21 games, then gave his life in the Armed Forces. Goaltending was the Rangers problem as Steve Buzinski, Jimmy Franks, and old veteran Bill Beveridge all had to face lots of rubber as the Rangers went from first to worst.

This was the last time that Boston defeated Montreal in a postseason series until 1988.

Note: GP = Games played, G = Goals, A = Assists, PTS = Points, PIM = Penalties in minutes

Source: NHL^[3]

Note: GP = Games played; Mins – Minutes played; GA = Goals against; GAA = Goals against average; W = Wins; L = Losses; T = Ties; SO = Shutouts

The following is a list of players of note who played their first NHL game in 1942–43 (listed with their first team, asterisk(*) marks debut in playoffs):

The following is a list of players of note that played their last game in the NHL in 1942–43 (listed with their last team):