Svindal edged his compatriot by little more than a tenth of a second in a breathless run down the piste at Jeongseon Alpine Centre to garnish a brilliant career with a gold medal at the age of 35.
With Jansrud grabbing the silver, four years after taking bronze in Sochi, the peerless duo continued Norway's outstanding record in the speed event.
The Scandinavian country has now medalled in the downhill in six of the last seven Olympics.
More good news travelled over from the Yongpyong Alpine Centre on Thursday, as Norway's Ragnhild Mowinckel claimed silver in the giant slalom behind champion Mikaela Shiffrin, the country's first Olympic medal in the event.
The plaudits rained down on Svindal as he became the oldest Olympic gold medallist in Alpine skiing, but he would have been equally happy with silver behind Jansrud.
"As Kjetil went down and I saw how fast he was, I was definitely preparing for a silver," he told reporters.
"I thought there's no way I can make up that time on the bottom.
"And that feeling was also a good feeling. So if I would've won silver I'd also be very happy still, so this gold is ... this is a special day for sure."
An emphasis on culture can be a cliche among elite sports teams, but for a small country like Norway, it's imperative, according to Norway Alpine team director Claus Ryste.
"We are a small nation with very little resources and we have to keep it tight and real," he told reporters.
“The team shows its strength, the coaches and the other athletes. I think the strength that Kjetil, Aksel and Aleks (Aamodt Kilde) have together also makes us stronger than the others."
Attention to detail also seems to be key, as anyone who would care to listen to Ryste's exhaustive analysis of the quality of the local snow and its effect on his skiers' performances would attest.
Being so dry, the snow crystals were sharp and "grippy", he said, requiring brute strength from his skiers not to dig down on the edges of their skis and be slowed.
"I think strong physical training is the secret. (A) strong physical condition programme keeps you more healthy," added Ryste.
Despite a litany of serious injuries through his long career, none were stronger than Svindal on the piste and his longevity is inspiring for 32-year-old Jansrud.
"Normally you can go until you are 36, 37 but it's all about the health, your mindset, if it's fun, if you are fast naturally," he said.
"Aksel can ski for many years to come and still be fast.
"I am excited for what is to come. I can't promise four more years but with the track record (we have) it seems like a good idea to try."
(Editing by Ed Osmond)
