Warholm, who set the world record of 45.94 seconds at the Tokyo Olympics, was running his first race of the season but destroyed the field and, even with a slight stutter off the final barrier, came home in 46.52, the fourth fastest time in history.
It was quicker than the 46.70 time he set two years ago on the same track that was then a world record.
American CJ Allen was second in an impressive personal best of 47.58.
"When you're on the track, you're in the bubble but I really felt the crowd lift me in the home straight - the adrenaline was really pumping in the last 100m," Warholm said.
"It was a race I will always remember - I felt really good today and knew something special was coming.
"Today shows in the right circumstances, I can really attack the world record, maybe even this year. It really sucked to be out injured last year and I wanted to make sure I came back with a big boom."
Ingebrigtsen, who set an all-time world best over two miles last week in Paris, was back on more familiar ground with the 1,500m and ran his trademark controlled race to come home in 3:27.95 - moving up to sixth in the all-time list with another European record.
The first eight finishers all broke 3.30 - six of them with personal bests - and third-placed Yared Nuguse set an American record of 3:29.02.
"The race went as expected, running by myself as usual, and the crowd was amazing, it was an incredible experience," Ingebrigtsen said.
"I 100% have more left in me. It's all about consistency in all of the races."
PHOTO FINISH
The crowd loved it and also appreciated a brilliant men’s 5,000m that came down to a photo finish as Yomif Kejelcha of Ethiopia and Ugandan Jacob Kiplimo both clocked 12.41.73 - the fifth-fastest of all time.
Kiplimo patiently sat on his rival’s shoulder until the final bend but after he surged ahead, Kejelcha responded as the Bislet Stadium fans roared them home. They both dipped for the line like sprinters and Kejelcha was given the decision by less than a hundredth of a second.
At the other end of the distance scale, Marie-Josee Ta Lou continued to fly the flag for the "older" sprinters as the 34-year-old Ivorian scorched to a world-lead 10.75 seconds in the women’s 100 metres - beating Marion Jones’s meeting record of 10.82 that had stood for 25 years.
Anthonique Strachan of the Bahamas was an impressive second in a personal best 10.92, edging out world 200m champion Jamaican Shericka Jackson (10.98).
Erriyon Knighton roared off the bend and piled it on in the final 50 metres for a hugely impressive time of 19.77 to win the men’s 200 metres and secure a hat-trick of victories on his European tour.
The 19-year-old is developing into a monumental talent and was well clear of Cuban Reynier Mena (20.09), with struggling Olympic champion Andre De Grasse back in fifth in 20.33.
South Africa’s former world and Olympic champion Wayde van Niekerk made a winning return to the circuit after years of injury problems, setting off strongly and holding on to win the 400 metres in 44.38 seconds - his first Diamond League victory in six years. Zambia’s 20-year-old prospect Muzala Samukonga, 10 years the winner’s junior, finished strongly in 44.49 for second place.
Ethiopian 17-year-old Birke Haylom put down a marker with a confident display of front running in the rarely-raced women’s mile as she broke clear halfway through the third lap, held her 10-metre lead through the bell and showed great strength to win in 4:17.13 - an Under-20 world record.
