Lemieux was selected first overall by the Pittsburgh Penguins in the in the 1984 NHL Entry Draft. He went on to win the Calder Memorial Trophy as best rookie, scoring 100 points. He has won the Art Ross Memorial Trophy six times as the league's leading scorer, the Hart Memorial Trophy three times as the league's most valuable player, and has been named to the NHL First All-Star team five times. Lemieux has topped the 100 point mark in a season 10 times, including a 199-point season in 1988-89.
Mario Lemieux led the Penguins to both of their Stanley Cup titles in 1990-91 and 1991-92 and was named the Conn Smythe Trophy winner in both of those years.
Lemieux was diagnosed with Hodgkin's disease, a form of cancer, in 1993. He retired due to chronic back problems following the 1996-97 season, but returned to the NHL in December 2000, after becoming the principal owner of the Penguins. In his return, he got an assist 30 seconds into his first shift. Despite playing in little more than half of the Penguins' games in 2000-01, he was one of the three finalists for the Hart Memorial Trophy that season.
A member of the Canadian Men's Olympic Gold Medal hockey team in 2002, Lemieux was second on the team with six points in six games.
Lemieux is widely considered to be one of the five greatest hockey players of all time. Following his sudden retirement in 1997, he was inducted into the Hockey Hall of Fame, as the usual three-year waiting period was waived.
| Season | Team | League | GP | G | A | Pts | PIM | Playoffs GP | G | A | Pts | PIM |
| 1981-82 | Laval Voisins | QMJHL | 64 | 30 | 66 | 96 | 22 | -- | -- | -- | -- | -- |
| 1982-83 | Laval Voisins | QMJHL | 66 | 84 | 100 | 184 | 76 | 12 | 14 | 18 | 32 | 18 |
| 1983-84 | Laval Voisins | QMJHL | 70 | 133 | 149 | 282 | 92 | 14 | 29 | 23 | 52 | 29 |
| 1984-85 | Pittsburgh Penguins | NHL | 73 | 43 | 57 | 100 | 54 | -- | -- | -- | -- | -- |
| 1985-86 | Pittsburgh Penguins | NHL | 79 | 48 | 93 | 141 | 43 | -- | -- | -- | -- | -- |
| 1986-87 | Pittsburgh Penguins | NHL | 63 | 54 | 53 | 107 | 57 | -- | -- | -- | -- | -- |
| 1987-88 | Pittsburgh Penguins | NHL | 77 | 70 | 98 | 168 | 92 | -- | -- | -- | -- | -- |
| 1988-89 | Pittsburgh Penguins | NHL | 76 | 85 | 114 | 199 | 100 | 11 | 12 | 7 | 19 | 16 |
| 1989-90 | Pittsburgh Penguins | NHL | 59 | 45 | 78 | 123 | 78 | -- | -- | -- | -- | -- |
| 1990-91 | Pittsburgh Penguins | NHL | 26 | 19 | 26 | 45 | 30 | 23 | 16 | 28 | 44 | 16 |
| 1991-92 | Pittsburgh Penguins | NHL | 64 | 44 | 87 | 131 | 94 | 15 | 16 | 18 | 34 | 2 |
| 1992-93 | Pittsburgh Penguins | NHL | 60 | 69 | 91 | 160 | 38 | 11 | 8 | 10 | 18 | 10 |
| 1993-94 | Pittsburgh Penguins | NHL | 22 | 17 | 20 | 37 | 32 | 6 | 4 | 3 | 7 | 2 |
| 1995-96 | Pittsburgh Penguins | NHL | 70 | 69 | 92 | 161 | 54 | 18 | 11 | 16 | 27 | 33 |
| 1996-97 | Pittsburgh Penguins | NHL | 76 | 50 | 72 | 122 | 65 | 5 | 3 | 3 | 6 | 4 |
| 2000-01 | Pittsburgh Penguins | NHL | 43 | 35 | 41 | 76 | 18 | 18 | 6 | 11 | 17 | 4 |
| 2001-02 | Pittsburgh Penguins | NHL | 24 | 6 | 25 | 31 | 14 | -- | -- | -- | -- | -- |
| 2002-03 | Pittsburgh Penguins | NHL | 67 | 28 | 63 | 91 | 43 | -- | -- | -- | -- | -- |