In a memorable race twice postponed since Sunday because of fog, Svendsen and Frenchman Fourcade reached the final straight together but the Norwegian seemed to have sealed victory when he pulled away in the sprint for the line.
But Fourcade, who had earlier claimed the 20km individual and 12.5km pursuit titles, fought back to lunge towards the finish - the first binding to cross the line determining the winner - just as Svendsen raised his arms in celebration.
The official television feed initially showed Fourcade as the winner but after a photo finish was called Svendsen was awarded the victory.
Svendsen, the 2010 Games' 20km individual and relay gold medalist, had a tough start to the Sochi Olympics but made up for it on Tuesday.
"At the beginning of the Olympics it was very tough because I had problems with my skis, but we are back where are supposed to be," Svendsen said.
"It might have looked like I could lose gold, but I had good control over him. I knew I would get gold. It looked closer than it was. I looked at the finish photo and was surprised how close it was.
"Martin is first of all a very good and honest guy. When he loses he is a much better guy than me when I lose. He is one of the most respected athletes in the field."
Fourcade, who said he only decided to compete at the last minute as he was suffering from sinusitis, said Svendsen deserved to win.
"He's usually faster than me on a sprint and it's not the first time he's beaten me on a photo finish, but many times I've made him crack at the shooting," said the Frenchman.
"We've been racing and competing together for three years now. Of course I imagined myself on the golden podium once in a while, but today he was a better biathlete.
"He has been the leader of this sport for four years now. I am right there behind him, but you could say that today - close, but not there."
The Frenchman also had to deal with rifle problems on the first shooting.
"The first three bullets did not go out so I had to reload three times," he explained.
Czech Ondrej Moravec took the bronze and he knew it was the best he could hope for.
"They were much stronger than me," he said.
"Emil went so strong and I could not react, but after that again we slowed down a little bit for just for a few metres, and then again in the stadium they pushed so hard and I had absolutely no chance."
Norwegian Ole Einar Bjoerndalen again missed out on a record 13th Winter Games medal when he made four mistakes at the final shooting and finished 22nd.
The start was delayed by 15 minutes because of snow before Fourcade and Bjoerndalen made one and two mistakes respectively on the first shooting.
Bjoerndalen made a huge effort to catch the leading group, which he paid for at the final standing shooting.
"I cannot explain it but it wasn't working today," said Bjoerndalen, who will have two other chances to beat the record he shares with compatriot and cross-country skier Bjorn Daehlie if he is selected for the relays.
"I felt strong in the tracks but the race is finished now and no changing that. I'm really down right now."
Fourcade now has two more opportunities to become the second Frenchman after Jean-Claude Killy (1968) to win three gold medals at a single Olympic Games.
He takes part in the mixed relay on Wednesday and the men's relay on Saturday.
"People have been talking a lot about it. In the Olympic village, (French cross-country) Robin Duvillard skier calls me Jean-Claude," he said with a smile.
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