Novak Djokovic branded his defeat by Jannik Sinner to end his long unbeaten Australian Open run as one of the worst performances of his career.
The world number one's 6-1 6-2 6-7 (6) 6-3 loss in the semi-finals was his first at Melbourne Park since a fourth-round defeat by Chung Hyeon in 2018, ending a 33-match streak taking in four titles.
Djokovic made 54 unforced errors, dropped serve five times and, for the first time in a completed grand slam match, did not create a single break point.
"First I want to congratulate Sinner for playing a great match, great tournament so far," said the Serbian, who had been chasing a record 25th slam title and 11th here.
"He’s deservedly in the finals. He outplayed me completely today. I was, in a way, shocked with my level, in a bad way. There was not much I was doing right in the first two sets.
"I guess this is one of the worst grand slam matches I’ve ever played. At least that I remember. Not a very pleasant feeling playing this way."
The 22-year-old Italian was seen as the most likely rival to stop Djokovic after beating him twice in two weeks at the end of last season at the ATP Finals and Davis Cup.
But surely no one would have predicted the manner of the first two sets of this semi-final, with an error-strewn Djokovic winning just three games.
He saved a match point in the third-set tie-break to give himself hope but there was no dramatic comeback, with Sinner regrouping impressively and going on to clinch victory after three hours and 22 minutes.
The fourth seed moves through to a first grand slam final while Djokovic must lick his wounds.
Djokovic struggled with illness at the start of the fortnight and had a tougher passage through to the last four than usual, losing three sets along the way.
Sinner, the first Italian to make an Australian Open singles final, had not dropped a set all tournament, and he started as he meant to go on, breaking the Djokovic serve to lead 2-0 with a searing forehand followed by a drive volley winner.
By contrast, nothing was working for Djokovic, with routine shots landing in the net or out of court, while he was also struggling on serve.
Sinner broke again to lead 5-1 and wrapped up the first set with just over half an hour gone.
Djokovic is a master at pacing himself in best-of-five-sets tennis and he would certainly not have panicked having lost only two of the last 17 slam matches in which he dropped the first set.
But the pattern of the match continued in the same vein, with more Djokovic errors helping Sinner break for 2-1 in the second set.
Djokovic whipped up crowd support after saving a break point at 2-4 in fine style but Sinner broke anyway two points later and served out the set.
Two years ago at Wimbledon, Sinner led Djokovic by two sets to love only to lose in five, so he knew very well that the match was far from over.
Djokovic, who had barely showed any emotion, clenched his fist after saving a break point in the opening game of the third set, and he at least managed to serve better.
At 5-5 and deuce on the Serbian’s serve, a medical emergency in the crowd forced a delay for several minutes, but Djokovic held his nerve on the resumption.
The world number one knew it was now or never in the tie-break, and he opened up a 4-2 lead, but Sinner surged back, creating a match point at 6-5 but netting a forehand, and a backhand over the baseline two points later gave Djokovic a lifeline.
He was still hanging on, though, saving three break points in the second game of the fourth set only to then be broken from 40-0 two games later.
Djokovic forced Sinner to serve it out but the Italian did not waver, clinching the biggest win of his life with a forehand winner.
