He won gold with a stunning effort in a sport that is traditionally dominated by European athletes.
"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 goes without saying. We were all in the wax room and just totally, totally happy."
Le Guellec, a native of Shannon, Que., finished the 10-kilometre sprint in 25 minutes 10.4 seconds after shooting clean. The previous best men's World Cup result by a Canadian was a sixth-place finish by Glen Rupertus in 1993.
France's Alexis Boeuf was second in 25:28.5 with one penalty and Austria's Christoph Sumann placed third in 25:35.2 with one penalty.
Le Guellec wasn't affected by the challenging shooting conditions that left most of the international field struggling.
"I was just trying to stay focused on skiing and stay relaxed," said Le Guellec. "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."
Zina Kocher of Red Deer, Alta., — the only other Canadian to reach the podium in a biathlon World Cup in the past two decades — finished 10th in the women's 7.5-kilometre sprint.
She finished in 22:20.2 with one missed shot, well back of Norway's Tora Berger. Ukraine's Olena Pidhrushna won silver and Russia's Olga Vilukhina earned bronze.
Le Guellec, 27, credits his support staff for keeping him calm and focused during his triumphant run.
"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,'" he said. "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's previous best result was a sixth-place finish in the sprint competition at the 2010 Vancouver Olympics.
His top result last season was an eighth-place finish in the sprint at Khanty Mansiysk, Russia. Le Guellec was 37th in the World Cup total score standings last season.
He will start first in the pursuit race on Sunday.
Kocher also celebrated her breakthrough in Oestersund, when she was third in the women’s individual competition in 2006. She became the first Canadian to reach an international biathlon podium since Myriam Bedard won double gold at the 1994 Winter Games.