As an amateur, St. Louis played for the University of Vermont Catamounts on the same team as Boston Bruins goaltender Tim Thomas, and on the same line as former Tampa Bay Lightning teammate Éric Perrin. St. Louis was an NCAA all-star and three-time Hobey Baker Award finalist for college player of the year. He ranks first amongst all Vermont scorers in career points (267) and assists (176), and ranks third in career goals (91). Despite his impressive numbers with the Catamounts, he was not drafted, and signed as a free agent with Calgary in 1998. He spent the latter part of the 1997–98 season with the IHL’s Cleveland Lumberjacks at the time of his signing with Calgary. He did put up impressive numbers with the Saint John Flames of the American Hockey League (AHL). When Craig Button was appointed GM of the Flames, he released St. Louis who then signed with the Tampa Bay Lightning.
St. Louis was on pace to have a career year in the 2001–02 when his season ended prematurely due to a broken leg. In 2003–04 he led the NHL in scoring with 94 points. He scored an overtime goal in Game 6 of the Stanley Cup Finals, helping the Tampa Bay Lightning defeat the Calgary Flames for the Stanley Cup. At season’s end he won both the Hart Memorial Trophy as the most valuable player to his team and the Lester B. Pearson Award as league MVP voted by his peers. St. Louis became the first player since Wayne Gretzky and only the eighth in NHL history, to win the Art Ross Trophy, the Stanley Cup, and the Hart Memorial Trophy all in one season.
In August 2005, Martin St. Louis signed a six-year deal with the Tampa Bay Lightning worth $31.5 million. St-Louis was quoted as saying, “I’m just happy that the Lightning have found a way to keep me long-term. Tampa was always my first choice, I’ve had so many good things happen to me in Tampa.”
St. Louis played for Team Canada at the 2004 World Cup of Hockey, where he was part of the team which won the World Cup, and the 2006 Winter Olympics which saw them eliminated by Russia in the quarterfinals after what was considered a disappointing tournament.
At the end of the 2007–08 season, St. Louis finished the season with 25 goals, 58 assists and 83 points, finishing second in team scoring behind teammate Vincent Lecavalier.
St. Louis was named finalist for the Lady Byng Trophy for the 2007–08 season and the 2008-09 season at the NHL Awards show in June. During the 2004–05 NHL lockout, he played for the Swiss team HC Lausanne.
At the end of the 2008-09 season, St. Louis finished the season with 30 goals, 50 assists and 80 points. He led the Tampa Bay Lightning in goals, assists, points, games played, and short handed goals. He was second in plus/minus and power play goals.
He and his wife Heather have three boys, Ryan, Lucas and Mason.
- ECAC All-Rookie Team – 1994
- ECAC All-Conference Team – 1994
- ECAC All-Star Team – 1995
- ECAC Player of the Year – 1995
- NCAA East First All-American Team – 1995
- ECAC All-Star Team – 1996
- NCAA East First All-American Team – 1996
- NCAA Championship All-Tournament Team – 1996
- ECAC All-Star Team – 1997
- NCAA East First All-American Team – 1997
- Played in 5 NHL All-Star Games – 2003, 2004, 2007, 2008, 2009
- Bud Light Plus/Minus Award (Co-winner with Marek Malik) – 2004
- NHL 1st All-Star RW — 2004
- Art Ross Memorial Trophy — 2004
- Lester B. Pearson Award — 2004
- Hart Memorial Trophy — 2004
- Stanley Cup Champion — 2004
- NHL 2nd All-Star RW — 2007