Born in Parry Sound, Ontario, Canada, Orr's ice hockey talents were evident at a very early age, and he was signed by Boston Bruins' scout Wren Blair at the age of twelve. As a 14-year-old he played for the Oshawa Generals in the junior league Ontario Hockey Association, competing against eighteen, nineteen and twenty-year-olds. National Hockey League rules dictated that he could not join the Boston Bruins before reaching eighteen. His third season he led the Generals to the OHA championship, and in his final season with Oshawa he averaged two points a game. Prominent Toronto lawyer Alan Eagleson negotiated his first contract with the Bruins. At the time it made Orr the highest-paid player in league history.

In his first professional season � although missing nine games with a knee injury presaging such woes throughout his career � Bobby Orr won the Calder Memorial Trophy as outstanding rookie and, while the perennially-cellar dwelling Bruins finished in last place that season, sparked a renaissance that propelled the Bruins to make the playoffs the following twenty-nine straight seasons, a North American professional sports record. New York Rangers' defenseman Harry Howell, the winner of the Norris Trophy as the league's best defenseman that season, famously predicted that he was glad to win when he did, because "Orr will own this trophy from now on."

Injuries limited Orr to just 46 games in the 1968 season, but he registered an amazing +65 for a resurgent third place team and won the first of eight straight Norris trophies. In 1970 he did the unthinkable, doubling his scoring total from the previous season to score 120 points, six shy of the league record and becoming the first (and to date, only) defenseman in history to win the Art Ross Trophy as the league's leading scorer. Besides the Norris and Art Ross, Orr also captured the first of his three consecutive Hart Trophies as regular-season MVP and he later win the Conn Smythe Trophy for his playoff heroics, being the only player in history to win four major NHL awards in one season. He went on to lead the Bruins in a march through the playoffs that culminated on May 10, 1970 when he scored one of the most acrobatic goals in hockey history to give Boston its first Stanley Cup in 29 years. The subsequent image of Orr flying through the air, his arms raised in victory � he had been tripped by Blues' defenseman Noel Picard at the moment of shooting � became a prize-winning photograph and is arguably the most famous and recognized hockey image of all time.

The following year, 1971, in a season where the powerhouse Bruins shattered dozens of league offensive records, Orr finished second in league scoring while setting records that still stand for points in a season by a defenseman and for plus/minus. He would lead the Bruins to the Stanley Cup again the following season, leading the league in scoring in the playoffs and scoring the championship-winning goal en route to his second Conn Smythe Trophy as playoff MVP.

His knee woes would take an increasing toll after 1972. Despite being limited by knee injuries which would later force him to retire early, he dominated the National Hockey League during his career, leading the Bruins to another first place league finish and the Stanley Cup finals in 1974. In a shortened career, he still won the James Norris Memorial Trophy as the league's most outstanding defenseman eight times, more than any other player in NHL history.

In 1976, despite several knee operations that left him playing in severe pain, Orr was named the most valuable player in the Canada Cup international competition.

At the end of the 1976 season, Orr's contract was over and the Boston Bruins needed to renew it. The Bruins offered Orr a lucrative contract, including over 18% ownership in the Bruins organization. However, Eagleson, who by this time was doubling as Orr's agent and executive director of the NHLPA, falsely told Orr that the Chicago Black Hawks had a better deal, something that was not revealed for a number of years. It later emerged that Eagleson had very good relations with Chicago's management, and frequently acted contrary to the interests of his clients in favor of teams whose management he favored.

Orr subsequently signed with Chicago, but his injuries rendered him too severely hurt to play, and � after playing in only 26 games over the next three seasons � retired in 1979. Famously, he never cashed a Chicago pay cheque, stating that he was paid to play hockey and would not accept a salary if he wasn't playing.

Orr retired having scored 270 goals and 645 assists in 657 games, adding 953 penalty minutes. At the time of his retirement, he was the leading defenseman in league history in goals, assists and points, 10th overall in assists and 19th in points. The only players in league history scoring more points per game than Orr are Wayne Gretzky, Mario Lemieux and Mike Bossy.