Johaug triumphed by 1min 43.3sec from American Jessie Diggins - the second-largest margin of victory in the history of the event.

Only compatriot Marit Bjørgen by 1:49.5 at Pyeongchang 2018 had won by a great advantage as Johaug continued Norway’s cross-country skiing dominance with an emphatic performance in Zhangjiakou.

The 33-year-old’s victory adds to her success in the women’s 10km classic and 15km skiathlon as she joins biathlon specialist Marte Olsbu Røiseland of Norway and speed skater Irene Schouten of The Netherlands as the only female athletes to win three gold medals in Beijing.

"I am so proud and I am so happy," said Johaug.

"It is a dream come true that I can stand here for Norway with three gold medals in the same Olympics.

"I was so, so happy 14 days ago when I got my first one [gold medal], and I cannot believe I should have more.

"It's fantastic to end my Olympic career with these three gold medals."

Johaug stormed clear to win the mass start freestyle in 1:24:54.0 as Diggins came a distant second in 1:26.37.3.

There were seven seconds separating the next six athletes, with Finland’s Kerttu Niskanen claiming bronze in 1:27:27.3.

The Niskanen family achieved five medals in Beijing, with her brother, Iivo Niskanen securing gold, silver and bronze.

"I am happy that he made an amazing Olympics here," said Niskanen.

"The whole family is waiting for us at home."

Diggins revealed that she had suffered from food poisoning 30 hours before her race.

"I thought I was going to die at the finish line," added Diggins.

"It was so special to see my family and my fiancé right afterwards on video.

"My legs were cramping the whole last 17 kilometres.

"I don't know how I made it to the finish.

"It was amazing."