Francesco Pellegrino of Italy took silver and Finland's Lauri Vuorinen the bronze in the men's race, while Norway's Kristine Stavaas Skistad claimed silver and Nadine Faehndrich won a surprise bronze for Switzerland in the women's event.
In front of thousands of cheering Norwegian supporters, Klaebo seemed unfazed as he waited at the start, and he quickly settled into his rhythm at the front of the field in pursuit of his fourth straight world title.
He briefly allowed Pellegrino to set the pace before easing past him around the halfway point and attacking on a punishing uphill stretch, building up just enough of a lead to hold off the strong challenge of the Italian.
Realising he couldn't be caught on the final straight, Klaebo eased up before the finish line to celebrate with the jubilant crowd as he finished in a time of two minutes 45.74 seconds, 0.67 seconds ahead of Pellegrino.
Finland's Vuorinen, who has previously only made two individual podiums in his 12-year career, had the race of his life as he held off the challenge of France's Jules Chappaz to claim the bronze by a margin of two-tenths of a second.
In the women's race, Swedish sprint queen Sundling dominated en route to her third straight world title, bursting out of the gate in a furious start before taking over and accelerating away to win in a time of three minutes 3.36 seconds, 2.2 seconds ahead of Norway's Stavaas Skistad.