The Shannon, Que. native finished the course in 25 minutes 10.4 seconds after a perfect run in the shooting range and a dominant 10-kilometre sprint.
The win in Sweden was also Le Guellec's first career victory.
"It is a huge, huge day," said Le Guellec. "I’m still surprised this actually happened. I’m definitely happy. It is just crazy. Everyone on the team is just ecstatic. That goeswithout saying. We were all in the wax room and just totally, totally happy."
The 27-year-old, who finished sixth in the 10-kilometre sprint at the 2010 Winter Olympics, came in sharp with the rifle and didn't miss a target during the shooting, while consistent skiing sent him to the top of the podium.
"My coach said to me the day you’ll be on the podium is the day you’ll expect it the least. Just go out there and do what you do — ski smooth, stay relaxed, and shoot every target one at a time," said Le Guellec. "That is exactly what I did today. The first lap I started to tense up a bit, but I told myself to just have fun, be relaxed and stay smooth. Those were the key words for the whole race. It finally happened and hopefully this is momentum for the rest of the season."
Le Guellec kept his cool during the sprint and did not anticipate a gold medal despite the flawless shooting round.
"I was just trying to stay focused on skiing, and stay relaxed. Until the last split, the coaches just kept saying that I was doing good. So I was a bit surprised when they told me on the last lap that I was first."
Alex Boeuf of France finished second, 18.1 seconds behind the Canadian, while Austrian Christoph Sumann took the bronze, 24.8 seconds off the leader.
Le Guellec's feat was Canada's major success in the sport since Myriam Bedard took two gold medals at the Olympics in Lillehammer 1994.