He clocked 40 minutes 02.78 seconds over the twisting two-lap 34.2 km circuit around the coastal city some 80 km south of Sydney and then waited as a string of feted champions completed the course.
None of them was able to better his time, however, with Swiss Stefan Kueng coming up 2.95 seconds short to take the silver and Belgian Remco Evenepoel, fresh from his Vuelta a Espana triumph, third in 40:11.94.
"It really feels like I'm in some kind of dream, I don't believe it, it's so unreal," said Foss, who will wear the rainbow jersey for the next year.
"My legs were really good and I was confident my shape was good shape but man, this is more than I can ever dream of.
"I'll really try to enjoy it but first I must realise it.
"I have to say, if I were top 10 today, I would be really, really satisfied, top five I was hoping for.
"To wear that jersey will be really, really special. I will try to honour it as best I can, and I will try to enjoy it as much as possible."
Foss will be only the second Norwegian to wear a rainbow jersey won in an elite race after Thor Hushovd, who triumphed in the road race at Geelong in 2010 the last time the championships were held in Australia.
Foss also believes that the Wollongong course, which featured 24 corners on each of the two laps of a circuit around the suburbs and up into the coastal hills of the city, had suited him.
"There was no real time to rest or to put down the power, you had to be really technical and push through the corners," he added.
"It was really about using the terrain and going hard where the gradients were a bit steeper and taking a rest where it went a bit faster.
"I had really good coaching and we prepared really well and so it was a perfectly executed race."
Foss was the 39th of the 50 riders to go out, which left him with a long wait as the likes of twice Tour de France winner Tadej Pogacar, Evenepoel and double defending champion Filippo Ganna completed the course.
"I wouldn't say I'm the guy with the most confidence, I really didn't believe it until it was over," said Foss.
"I put everything out there today, I couldn't have done anything better. I had to be satisfied and then the other guys had to do their race. But man, this is unbelievable."
Italian Ganna, who was looking for a third straight title, finished seventh behind Pogacar of Slovenia in sixth.
The rider who will be most cursing his luck was Briton Ethan Hayter, who finished fourth nearly 40 seconds behind Foss despite losing his chain riding over a bump in the road and having to change bikes in the middle of the race.
It was the first time that the women and men had competed on the same world championship time trial course over the same distance on the same day and Ellen van Dijk earlier retained her title.
The 35-year-old Dutchwoman clocked 44 minutes 28.60 seconds over to pip early starter Grace Brown of Australia by 12.73 seconds and claim her third world title. Swiss Marlen Reusser won bronze to add to her silvers from the last two editions.
The gold medal made Van Dijk the second most successful rider in the history of the women's world championships behind France's Jeannie Longo, who won four time trial titles between 1995 and 2001.
"I just thought I've had a great year in the rainbow jersey and I'll just give it all today," said van Dyke, who claimed her first title in 2013.
"I had no idea how I was riding. Honestly, I was so surprised when I crossed the finish line."
Italy's Vittoria Guazzini finished fourth to take the inaugural women's under-23 title.
