Rafael Nadal produced some scintillating tennis to come from one set down to beat Roger Federer and reach his second Australian Open final.
The world number two, who won the 2009 title, lost an opening set tie-break but hit back to take the next three and win 6-7 (5-7) 6-2 7-6 (7-5) 6-4.
Third seed Federer saved one match point on Nadal's serve but the Spaniard held his nerve to take it on the next.
Nadal will play either Andy Murray or Novak Djokovic in Sunday's final.
It was another classic encounter in what remains one of sport's greatest rivalries, with the 10-time Grand Slam champion Nadal extending his winning record over Federer to 18 victories in 27 meetings.
The Mallorcan gave his best wishes to his defeated opponent after what he described as "another fantastic match".
Nadal, who injured his knee prior to the tournament, added: "Sunday afternoon, 24 hours to play my first match, I was in my room crying because I believed I didn't have the chance to play in Melbourne.
"So it was a very, very tough situation for me, those hours.
"Two weeks later I am here in the finals, so it is a dream for me because I had very bad expectations 24 hours before the first match, and now two weeks later I am playing well. I am in the final.
"Always playing Grand Slam finals is very good news. I've been in the last four Grand Slam finals so it is a great effort I think."
Federer, bidding for a 17th Grand Slam title, started imperiously, breaking Nadal early to take a 3-0 lead only for the tenacious Spaniard to bite back to take the first set to a tie-break.
The four-time champion looked in control of the match until he relinquished his early break, with Nadal restoring parity in the seventh game thanks to a wonderful passing shot.
A mini-break was enough to ensure the 30-year-old Swiss prevailed to claim the opening set, but Nadal bounced back with vengeance to break his rival in the fifth game of the second set for an unassailable lead.
With Nadal leading 5-2 in the second set, the players had to take a 10-minute break for an Australia Day fireworks display, which seemed to affect Federer the most as he dropped his service game.
"It's tough, it's not helpful, that's for sure,'' Federer said of the break. "They told us before, so it was no surprise. But I knew it was a lot of points in a row that I lost.'"
Federer's play was becoming increasingly wayward - he ended the match with 63 unforced errors compared with Nadal's 34 - as he tried in vain to fathom a way of penetrating Nadal's stubborn defence.
Both players' service games faltered in the third set. The pair exchanged breaks before taking the set to a tie-break, with Nadal coming out on top despite Federer valiantly saving five set points.
The second seed went on to secure a crucial break in the ninth game of the final set to serve for an impressive win, which ended Federer's 25-match winning run.
"I haven't lost in five months or something so it's not that bad," said Federer. "Don't feel too sorry for me.
"Obviously I would have loved to have come through and gotten a crack, a chance at winning the title here again.
"I thought Rafa played well from start to finish. It was a tough match physically as well. I'm disappointed, but it's only the beginning of the season. I'm feeling all right so it's ok."