The veteran goaltender is the second player from the national team to recently announce her retirement after forward Sarah Vaillancourt of Sherbrooke, Que., did the same last week.
While Vaillancourt's decision was a surprise, St. Pierre's announcement was more of a formality.
The 34-year-old from Chateauguay, Que., took the 2011-12 season off to have a baby boy, Liam, with fiance Lenny Jo Goudreau.
St. Pierre returned to play goal this past season for the Montreal Stars of the Canadian Women's Hockey League, but she hasn't played for Canada since the 2011 world championship.
Hockey Canada is expected to soon name a roster of 27 women who will try out for the 2014 Olympic team, so St. Pierre decided it was time to make her future plans known.
"Being part of three Olympic teams and nine world championship teams, I think I accomplished everything that I wanted to accomplish," St. Pierre told The Canadian Press on Monday. "That's why I retire today with a big smile."
St. Pierre won Olympic gold in 2002, 2006 and 2010. She was Canada's starting goaltender in world championship finals from 2001 to 2008 and was named the tournament's top goalie in both 2001 and 2004. In her nine world championships, she won gold five times.
But her 25-save performance in the final of the 2002 Olympic women's hockey tournament stands out. Canada won women's Olympic hockey gold for the first time in an emotional 3-2 win over the United States in Salt Lake City. That win also snapped Canada's eight-game losing streak against the Americans.
"The 2002 Olympics I think will always be the favourite moment of my career," she said. "To be able to come back from eight losses against the U.S. and winning against them and getting my first gold medal with my parents being in the stands, I think that will always be my favourite memories of all my years with Team Canada."
St. Pierre is Canada's all-time leading goaltender in games (83), wins (64) and shutouts (29).
Earning a goaltending job on the national team and keeping it is difficult because there is so much competition for only three spots. When St. Pierre was Canada's starter, the roster was limited to just two goalies.
Edmonton's Shannon Szabados took over as Canada's No. 1 during the 2009-10 season and has started Olympic and world finals since then.
St. Pierre says motherhood and the various career opportunities in front of her helped prepare her for life after hockey.
"I think I was really prepared, starting from the year I had to take off because I was pregnant," she explained. "That made me realize what it would feel like to not be a hockey player any more. I kind of missed it, which is why I wanted to try and come back for at least a season.
"I did my comeback. I did what I had to do, but now I'm at a point where I have no regrets. I was so lucky and privileged to live my dream for so many years of putting on the Team Canada jersey year after year, for 13 years I think."
St. Pierre is pursuing a career in real estate and wants to have more children. She's helping a friend with a girls' hockey school and expects to do some television work in the future.