Joseph Gérard Marquis Tardif (born June 12, 1949) is a Canadian former professional ice hockey player. He played left winger in both the National Hockey League (NHL) and the World Hockey Association (WHA), principally for the Quebec Nordiques. He also represented Canada in the 1974 Summit Series. A dominant force in the WHA, Tardif had four consecutive seasons with 95+ points from 1975 to 1979 and served as the first captain of the Nordiques when they joined the NHL. On April 4, 1978, he became the second professional hockey player to record 150 points in a season. In addition to his two Stanley Cup championships, he also won the Avco World Trophy to go along with winning the Gordie Howe Trophy for most valuable play in the WHA (1976, 1978).

Tardif finished as the all-time leading goal scorer in the WHA, scoring 316 goals in 446 games. In his professional career between the two leagues, Tardif scored 510 total goals.

Born in Granby, Quebec, Tardif honed his skills for local school leagues in the winter, first playing as the age of five. He was recruited to play for Collège Laval, a private school, at the age of 14. A year later, Canadiens scout Ron Caron signed him to a deal with the farm team of the Montreal Junior Canadiens with the Thetford Mines Canadiens, where he met fellow future NHLers Rejean Houle and Gilbert Perreault.

Tardif played two seasons with the Montreal Junior Canadiens of the Quebec Major Junior Hockey League (1967-1969), winning the Memorial Cup in 1969 with Houle and Perreault on the team. The Montreal Canadiens, in the final year the National Hockey League team had the privilege to do so, invoked its right to select two French Canadian players first and second overall in the 1969 NHL Amateur Draft, with Tardif being selected second while Houle went first. Tardif spent most of the 1969–70 season with the American Hockey League (AHL) for the Montreal Voyageurs. He was one of the leading scorers on a team studded with future NHL stars, including Jude Drouin, Guy Charron, Guy Lapointe and Pete Mahovlich.

Tardif played eighteen games of the 1969–70 season, with his first game on October 11 seeing him earn a ten-minute misconduct penalty for exchanging words with referee (and future WHA mainstay) Bill Friday. He recorded his first goal on October 19 against the Philadelphia Flyers off Bernie Parent. He made the Canadiens for good the following season, playing credibly for the eventual Stanley Cup champions with 19 goals and 30 assists in 76 games. He logged three goals and an assist in the 1971 Stanley Cup playoffs as the Canadiens won the Stanley Cup. In 1972, Tardif scored 31 goals. Troubles with head coach Scotty Bowman led to speculation about Tardif's future in Montreal by the beginning of 1973. He closed his Montreal career out with a second Stanley Cup championship in 1973, scoring the final goal of the decisive Game 6.

On June 5, 1973, Tardif signed a three-year contract (speculated to be over $350,000) with the Los Angeles Sharks of the World Hockey Association, one that gave him what he wanted most: a long-term, no-trade, no-cut contract. Tardif specified later that he signed with the league rather than the team, as the way business was done with them involved the money being guaranteed but the full amount for the first year was deposited in a New York bank. Despite taking until his 10th game to score a goal, he was the Sharks' leading scorer that season, and was named to play for Team Canada in the 1974 Summit Series the following fall. The Sharks, however, finished with the league's poorest record, and moved to Detroit as the Michigan Stags in April 1974.

In July of that year, Tardif was selected to play on Team Canada for the 1974 Summit Series, which exclusively had WHA players play the Soviet Union prior to the start of the 1974 WHA season, although he had to miss the start of the series due to attending to his wife, who was due to give birth to their son. Joining the team in the Russia portion of the series, Tardif recorded one total point. In the Stags home opener on October 29, Tardif scored a goal that tied the game (which ended up with a win in overtime) but found himself booed, with team executives speculating that Michigan fans naturally get on "superstars". By December, there were rumblings of the franchise possibly folding or relocating. On December 7, Tardif, alongside Steve Sutherland, were traded to the Quebec Nordiques in exchange for Pierre Guité, Alain Caron, and Michael Rouleau (the Stags moved to Baltimore in January and folded after the season ended).

In Quebec, Tardif became one of the league's preeminent stars. He finished the 1974–75 WHA season with 50 goals and added a league-leading 10 goals in the playoffs on the road to the Avco Cup Final against the eventual champion Houston Aeros. On December 8, 1975, Tardif signed a contract with Quebec for ten years that was estimated to be worth $1.6 million. Tardif immediately became an icon for the French Canadian locale. The next season, he led the WHA in goals, assists and points by wide margins and became only the third professional player to score 70 goals in a single season (after Phil Esposito and Bobby Hull), while the Nordiques rampaged to 50 wins. Tardif's playoffs were cut short after he incurred serious head injuries in an attack during Game 2 of the Quarterfinals matchup on April 11 against the Calgary Cowboys by enforcer Rick Jodzio, leading to one of the first cases where a hockey player was charged in a court of law for assault. Tardif did not skate for four months and dealt with dizzy spells for a time. So incensed were the Nordiques that they threatened to not play the rest of the playoffs unless the league agreed to their three demands (a lifetime suspension of Jodzio, the suspension of Calgary coach Joe Crozier and the resignation of WHA executive Bud Poile; Quebec ultimately played while Jodzio and Crozier were issued suspensions). On May 26, 1976, Tardif was awarded the league MVP. Tardif stated in later years that the brawl made him a "more careful player" and teammates stated he was never the same player.