Bjørgen crossed the line in 1 hour 11 minutes 5.2 seconds, with Therese Johaug finishing 2.6 seconds later to claim silver.
Their compatriot Kristin Størmer Steira came in third, a further 21.0 seconds back for bronze, thus completing a Norwegian 1-2-3.
The chasing pack was headed by Finland’s Kerttu Niskanen who finished fourth and almost a full minute off the podium.
The wily Bjørgen timed her race to perfection, coming from behind to overtake Johaug on the final climb and take her Sochi gold tally to three, following earlier wins in the skiathlon and team sprint.
“It's incredible,” said a delighted Bjørgen at the finish. “We're all Norwegian and we're all on the podium. This has been a goal for me for a long time.
“I thought the 30km would be hard but I've felt very good in the last days.”
The 33-year-old, known as “Gull-Marit” (“Golden Marit”) in her home country, now boasts six Olympic golds in total – putting her on a par with speed skater Lidia Skoblikova (URS) and fellow cross-country skier Lyubov Yegorova (URS).
She also now has 10 medals overall accumulated during four appearances at the Winter Games; it is a tally only matched by two other women: fellow cross-country skiers Raisa Smetanina (URS) and Stefania Belmondo (ITA).
The Norwegian trio had dominated from early, breaking free from the pack at the 10km mark.
They then raced in compact formation, taking it in turns to lead, with each racer dropping back into the slipstream, all three conserved their energy for the final push.
In the last few kilometres FIS World Cup leader Johaug made a break for it. Bjørgen stayed on her shoulder, as Steiria faded and fell back.
It was now a two-woman race, and was all about which of the two heavyweights could squeeze out a last burst of energy and inspiration. The final ascent proved decisive, as Bjørgen kicked on, overtaking Johaug, who could not muster a meaningful response.
Earlier in the tournament the Norwegian team had complained of problems with their skis, and had finished a disappointing fifth in the relay.
But they had clearly put such concerns behind them in this race, with all three frontrunners foregoing the customary option to swap their skis at the 20km mark.
“It means a lot to the team,” said Johaug. “We have come back from the relay. We knew we were stronger than that. We had very good skis, the waxing team did a great job.”
“We weren't that good in the relay so we showed today that we are the best,” added Bjørgen, who now has every right to be regarded as the best on an individual basis too.
In the course of four appearances at the Winter Games, the Norwegian has now secured a podium finish over every distance on the Olympic programme contested by women, underlining her credentials as the best female all-rounder of all time.