The history of the New York Islanders National Hockey League team dates back to 1972. Since 1980, the franchise has played in five Stanley Cup Final, winning four straight Stanley Cups from 1980 to 1983.

1972–1974: The NHL heads to Long Island

With the impending start of the World Hockey Association (WHA) in the fall of 1972, the upstart league had plans to place its New York team, the Raiders, in Nassau County's brand-new Nassau Veterans Memorial Coliseum. County officials did not consider the WHA a major league and wanted to keep the Raiders out. William Shea, who had helped bring the Major League Baseball's New York Mets to the area a decade earlier, was enlisted to bring an NHL team to Long Island. Shea found a receptive ear in NHL president Clarence Campbell but faced opposition from the New York Rangers, who didn't want additional competition in the New York area. Eventually, Campbell and Shea persuaded the Rangers' owners, Madison Square Garden, to reconsider. Rangers' president Bill Jennings realized that he had two choices. If he allowed another New York-based NHL team, he would at least be able to extract compensation from it for sharing the Rangers' NHL territory. In contrast, a WHA rival would not be obligated to pay the Rangers anything. Perhaps remembering the crucial role the New York Jets had played in ensuring the success of the American Football League just a few years earlier, Jennings ended up helping to bring a new NHL team into town. Despite expanding to 14 teams just two years prior, the NHL hastily awarded a Long Island-based franchise to clothing manufacturer Roy Boe, owner of the American Basketball Association's New York Nets, on November 8, 1971. The terms of the franchise included $6 million ($ million in dollars) franchise fee plus a $5 million ($ million in dollars) territorial fee to the Rangers. An expansion franchise was also given to Atlanta (the Flames) to keep the schedule balanced.

The franchise chose New York Islanders as its name, although many expected it to choose the "Long Island Ducks", the name used by a team that played in the Eastern Hockey League from 1959 to 1973.NHL Team Nicknames Explained The team was soon nicknamed the "Isles" by the local newspapers. The Islanders' arrival effectively doomed the Raiders, who played in Madison Square Garden under difficult lease terms and were forced to move to Cherry Hill, New Jersey in the middle of their second season.

On February 14, 1972, Bill Torrey, executive vice president of the NHL's California Golden Seals, was named as the team's general manager. The Islanders secured veteran forward Ed Westfall, Gerry Hart, and goaltender Billy Smith in the 1972 expansion draft, along with junior league stars Billy Harris, Lorne Henning, and Bobby Nystrom in the 1972 amateur draft. Soon after the draft, Phil Goyette was named as the team's first head coach, however he was fired halfway through the season and replaced with Earl Ingarfield and assistant coach Aut Erickson. Unlike most other expansion teams' general managers, Torrey made few trades for veteran players in the early years, as he was committed to building the team through the draft; he stated, "I told the owners that we're not going to beat this team next door by taking the castoffs from others teams. We'd have to develop our own stars." Before the season began, Westfall was named the team's first captain. Their first win came on October 12, 1972, in a 3–2 game against the Los Angeles Kings. In the team's first season, young players such as Smith, Nystrom, and Henning (all of whom would be part of the Islanders dynasty that would win four straight Stanley Cups in the 1980s) were given chances to prove themselves in the NHL. However, the young and inexperienced expansion team posted a record of 12–60–6, setting an NHL record for number of losses and worst overall record in a season. A rare highlight occurred on January 18 when they defeated the defending Stanley Cup Champion Boston Bruins 9–7.

Finishing last in the standings that season, they received the right to select first in the 1973 draft. Off the ice, the Islanders struggled financially, a situation that was exacerbated by the then unprecedented 11 million dollars in franchise and territorial fees. Montreal Canadiens' general manager Sam Pollock was keen to acquire the Islanders' pick so he could bring French Canadian junior star defenseman Denis Potvin, who had been touted as "the next Bobby Orr" when he was 14 years old, to Montreal. Pollock made several lucrative trade offers including cash to the Islanders, but Torrey turned the Canadiens down and selected Potvin with the first overall pick. During the off-season, Torrey convinced former St. Louis Blues coach Al Arbour to come coach the Islanders. Even with Arbour as the team's head coach and Potvin, who won the Calder Memorial Trophy as NHL Rookie of the Year, the team again finished last in the East Division that season, but allowed 100 fewer goals than the previous season. The season included their first win against the Rangers, on October 27, 1973, which also happened to be the game where Potvin scored his first NHL goal. Although they failed to make the playoffs, their 56 points represented a 26-point improvement from the previous season.

1974–1979: Ascendancy and playoff inability

With the fourth and twenty-second picks in the 1974 draft, the Islanders added young forwards Clark Gillies and Bryan Trottier to continue Torrey's building plan. In 1975, the Islanders made one of the biggest turnarounds in NHL history. Led by Potvin, forwards Westfall, Harris, Nystrom, Gillies, and goaltenders Smith and Glenn "Chico" Resch, the team earned 88 points, 32 more than the previous season and two more than their first two seasons combined, earning their first playoff berth. They defeated the rival New York Rangers in a best-of-3 first-round series as J. P. Parise scored just 11 seconds into overtime of the third game. In the next round, down three games to none in a best-of-seven series against the Pittsburgh Penguins, the Islanders rallied to win the next four and take the series, winning game seven on a late third period goal by Westfall. Only four other major North American professional sports teams have accomplished this feat (the 1941–42 Toronto Maple Leafs, Major League Baseball's 2004 Boston Red Sox, the 2009–10 Philadelphia Flyers, and the 2013–14 Los Angeles Kings). They were close but not as lucky in the following round, rallying from another 3–0 deficit to force a seventh game against the defending Stanley Cup champion Philadelphia Flyers before the Flyers took the decisive seventh game at home and went on to win the Cup again. Despite a disappointing playoff finish, Arbour remained complimentary of the team's attitude and maturity, saying "If I called a practice next week, every one of them would show up."

The Islanders continued their climb up the standings in 1975–76, earning 101 points and the fifth-best record in the league. It was the first 100-point season in Islanders history, in only their fourth year of existence. Rookie center Trottier finished the season scoring 95 points and winning the Calder Memorial Trophy; his points and assists (63) totals set a new league record for most in each category by a rookie. It would be the first of four consecutive 100-point seasons, including the first two division titles in franchise history. Despite the emergence of young star players and regular season success between 1976 and 1979 the Islanders suffered a series of playoff disappointments. In 1976 and 1977, the Islanders were knocked out in the semi-finals by eventual Stanley Cup champions, the Montreal Canadiens. The Canadiens posted a 24–3 record in the playoffs during those two years with all three losses coming from the Islanders.

In the 1977 draft, Torrey had the 15th overall pick and was deciding between forwards Mike Bossy and Dwight Foster. Bossy was known as an emerging scorer who lacked physicality, while Foster could check and had led the Ontario Hockey League in scoring. Arbour persuaded Torrey to pick Bossy, arguing it was easier to teach a scorer how to check. In the upcoming 1977–78 season, Bossy became the third Islander to win the Calder Trophy, having scored 53 goals that season, the most scored by a rookie at the time. The team earned their first Patrick Division and Campbell Conference championships. Six players finished the season with 30 goals scored or more, with five of them being players drafted by the Islanders, showing the success of the draft building process. The season ended with a familiar result as the team lost in the overtime during playoffs game seven of the quarterfinals against the Toronto Maple Leafs; Billy Harris failed on a breakaway which was followed by Lanny McDonald scoring to complete an upset.

In 1978–79, the team finished with the best record in the NHL, clinching it with three goals in the third period of the seasons final game against the Rangers. Trottier was voted the league MVP and captured the scoring title, while sophomore Bossy scored 69 goals, which also led the league. Despite their regular season dominance, the Islanders exited the playoffs with another upset playoff loss, this time to the Rangers in the semi-finals. As the team was leaving Madison Square Garden following their game six elimination, Rangers fans rocked and threw objects at the team's bus. Hockey professionals and journalists generally questioned whether the Islanders were capable of winning the important games needed to win a Stanley Cup. Islander players would cite fear of repeating the pain of this loss as spurring their later success. After surrendering the captaincy to Gillies the season before, Westfall retired and shortly thereafter became a color commentator on the team's telecasts.

Off the ice, the Islanders were on shaky ground. Boe was losing money on both the Islanders and the Nets even as the Islanders quickly surged to NHL prominence and the Nets became an American Basketball Association power. The Islanders were still far behind on the $10 million they had paid in startup costs, and the expenses associated with moving the Nets to the National Basketball Association threw Boe's finances into a tailspin. Eventually, Boe was forced to sell both his teams. He readily found a buyer for the Nets, but had less luck finding one for the Islanders. Torrey orchestrated a sale to one of the team's limited partners, John Pickett, who assigned Torrey as team president. Soon after purchasing the team, Pickett signed a very lucrative cable contract with the fledgling SportsChannel network as their owner, Charles Dolan, thought the up-and-coming Islanders would be a perfect centerpiece for his new network. Dolan gave Pickett a long-term guaranteed contract intended to not only keep the team on Long Island, but give area governments an incentive to renew his cable contracts. The Islanders have remained on the network, now known as MSG Plus, for over a quarter-century.

1980–1983: The Dynasty

After the Islanders' regular season dominance and playoff disappointment in 1979, Arbour decided that he would no longer concern himself too greatly with his team's finish in the regular season. Instead, he focused his team's energy on how they would perform in the playoffs. In 1980, the Islanders dropped below the 100-point mark for the first time in five years, earning only 91 points. However, they finally broke through and won the Stanley Cup.