It was Australia's first title in the event since Michael Rogers' winning ride in 2005, and Dennis did it in convincing style, beating defending champion Tom Dumoulin (Netherlands) into second place by a huge 1:21 over the 52.5km course, with Belgium's Victor Campenaerts finishing just half a second behind to take the third place on the podium.
Dennis' win comes after a successful season against the clock, with time-trial stage wins at both the Giro d'Italia and the Vuelta a España. He was nervous before the race about admitting that he was one of the favourites, having been burned in the past by mechanicals and crashes, but everything came together on the day, and the Australian now has a rainbow jersey for his troubles.
Campenaerts was thrilled to take the final step on the podium, and already has a champion's jersey to call his own after defending the European time trial title in Glasgow last month.
Dumoulin, however, was left disappointed by his ride for second place. The Dutchman has had an incredibly successful season, during which he's finished second overall at both the Giro d'Italia and the Tour de France, to Sky's Chris Froome and Geraint Thomas, respectively.
But he said after Wednesday's time trial that he was a "broken man", even though he had gone into the race with every intention of defending the title he won 12 months ago.
"But from the first kilometre, I was pretty sure it was not going to happen," he admitted. "I was just not at my top level today."
Dennis now has 12 months – during time trials, at least – in one of the sport's most prestigious jerseys. Both riders will now ride the men's road race on Sunday, and both riders will have another chance at winning some more rainbow stripes, even if they're not among the very top favourites.
Watch Dennis take his first time trial world title in the video highlights above.