The 1979–80 NHL season was the 63rd season of the National Hockey League. This season saw the addition of four teams from the disbanded World Hockey Association as expansion franchises. The Edmonton Oilers, Winnipeg Jets, New England Whalers (later renamed "Hartford Whalers" at the insistence of the Boston Bruins), and Quebec Nordiques joined the NHL, bringing the total to 21 teams. The other two WHA teams (Birmingham Bulls and Cincinnati Stingers) were paid to fold.

The New York Islanders won their first Stanley Cup, defeating the Philadelphia Flyers in six games, in the finals.

The season also marked the eighth and final season for the Flames in Atlanta before the franchise relocated to Calgary. The NHL would return to the Georgia capital in 1999 with the Thrashers, but that team would ultimately relocate away from Atlanta as well becoming the second (and current) incarnation of the Winnipeg Jets.

The collapse of the WHA also saw the much hyped super-star rookie Wayne Gretzky come to the NHL with the Edmonton Oilers. Gretzky would tie Marcel Dionne for the scoring lead with 137 points and capture the Hart Memorial Trophy as the most valuable player while Dionne took home the Art Ross Trophy as the leading scorer by virtue of having scored two more goals. Gretzky aside, many players made their debut in the NHL this season, both due to the WHA merger and to a change in the rules for the Entry Draft allowing eighteen- and nineteen-year-olds to be drafted for the first time; no fewer than seven Hall of Famers (Gretzky, Ray Bourque, Mark Messier, Mike Gartner, Michel Goulet, Mark Howe, and an undrafted Joe Mullen) debuted this season, along with numerous other perennial stars.

The big story of the regular season was the record-breaking undefeated streak compiled by the Philadelphia Flyers. After starting the season with a 5–2 win over the New York Islanders and a 9–2 loss to the Atlanta Flames, the Flyers did not lose again for nearly three months, earning at least one point in every game between a 4–3 win over Toronto on October 14, 1979, and a 4–2 win over Buffalo on January 6, 1980, earning a 35-game record of 25–0–10. This stands as the longest undefeated streak in North American professional sports history.

With 21 teams in the league, the regular-season schedule was set without regard to divisional affiliation. Each team played each of the other 20 teams four times in the year, twice at home and twice on the road. As well, a new playoff structure was introduced with the four division winners plus the next 12 teams with the best records qualifying. Division winners were not granted any byes and the divisions were ignored for determining playoff match-up seeding. Thus the division grouping ensured that if the five worst teams were to be in the same five-team division, the winner of this division would have qualified for the playoffs despite having the fifth worst season record. Except for that unlikely possibility, the divisional affiliations were irrelevant and had no effect on playoff qualification or seeding. A few months into the season, the Detroit Red Wings started playing at Joe Louis Arena after having spent all but their first season at the Detroit Olympia.

For the four previous seasons, the Boston Bruins had owned first place in the Adams Division. This season saw the Buffalo Sabres dethrone the Bruins in the Adams. The New York Islanders finished first overall in the NHL the previous season with 116 points, but lost in the playoffs semifinals to the upstart New York Rangers. This season saw them fall considerably in the standings as they finished fifth overall with 91 points, a full 25 points below last year's finish. On the other hand, the Philadelphia Flyers improved by 21 points from the previous season. Their 35-game undefeated streak (25–0–10) propelled them to the best record in the NHL with 116 points.

All four expansion teams finished poorly with records below .500. The Hartford Whalers fared the best with 73 points and the Winnipeg Jets tied the Colorado Rockies for last overall with 51 points. Hartford (14th overall) and Edmonton (16th overall) qualified for the playoffs, but both teams were swept 3 games to 0 in their respective first-round playoff series.

With the league expansion from 17 to 21 teams, the playoffs were also expanded, from a 12-team tournament to a 16-team tournament. The sixteen teams were composed of the four divisional champions plus the top 12 finishers of the remaining 17 teams. The 16 qualifying teams were then seeded based on regular season points, with divisional rankings ignored. Division leaders no longer received first round byes. The teams were seeded 1 through 16, with the top team playing the 16th team in the first round, and so on. In subsequent rounds, matchups were similarly arranged, with the top remaining seed against the lowest remaining seed, and so on. The preliminary round was a best-of-five set.^[2] The Atlanta Flames played their final playoff games in this postseason, and moved to Calgary soon after. The playoffs returned to Atlanta in 2007.

Hockey Night in Canada on CBC Television televised Saturday night regular season games and Stanley Cup playoff games.

In the U.S., the league dissolved the NHL Network, the national broadcast syndication package that aired games from the 1975–76 through the 1978–79 seasons. The fledgling cable networks ESPN and UA-Columbia (later known as the USA Network) each signed agreements to broadcast slates of regular season games. The Hughes Television Network, the NHL Network's former distributor, also signed a deal to syndicate a schedule of Thursday night regular season games, selected playoff games, and the first five games of the 1980 Stanley Cup Finals. CBS then agreed to televise Game 6 of the Cup Finals. That would be the last NHL game to air on U.S. network television until NBC televised the 1990 All-Star Game, as the league remained on national cable television for the rest of the 1980s.

• List of Stanley Cup champions
• 1979–80 NHL transactions
• 1979 NHL Entry Draft
• 1979 NHL Expansion Draft
• 32nd National Hockey League All-Star Game
• National Hockey League All-Star Game
• World Hockey Association
• List of WHA seasons
• Ice hockey at the 1980 Winter Olympics
• 1979 in sports
• 1980 in sports