Andy Murray came storming back after a poor start to beat Tomas Berdych and reach his fourth Australian Open final.
The British number one lost a tense first set but recovered to win 6-7 (6-8) 6-0 6-3 7-5.
It will be the sixth seed's eighth Grand Slam final and first working with Amelie Mauresmo, with ex-coach Dani Vallverdu now in Berdych's corner.
Murray, 27, will play the winner of Friday's semi-final between Novak Djokovic and Stan Wawrinka.
Highlights of Andy Murray vs Tomas Berdych
"There was a little bit of extra tension - it was a big match," said Murray. "A lot was made about Dani Vallverdu, my former coach, working with Tomas.
"But we've been friends since we were 15 years old and I felt that the focus was unfair and unnecessary.
"This is sport - and there's more to life than sport. It created a bit of extra tension but everyone calmed down after start of the match."
The Scot's hopes were under threat after losing a tension-filled opening set, but he turned it around with a brilliant lob early in the second and took control with seven straight games.
Berdych, 29, had started much the better and served for the set at 5-3, only for Murray to break straight back in a rally of huge forehands and celebrate wildly in the direction of the Czech's player box.
There was a definite edge to the contest, and some sharp words followed from Murray in the next game when Berdych complained about the balls.
Two more break points slipped by at 5-5 but Murray edged ahead in the tiebreak, earning the first set point, only for Berdych to save it impressively behind his serve and go on to clinch it.
The Czech, who beat Rafael Nadal for the first time since 2006 in the quarter-finals, then suffered an unexpected collapse as Murray's game began to flow.
A superb running lob, similar to the three he produced in his quarter-final win over Nick Kyrgios, helped Murray break for 2-0, and within half an hour he had taken the set to love.
Berdych, seeded seventh, got back on the scoreboard early in the third but it was Murray who was pressing, and the Czech's game crumbled horribly in game six.
From 40-0, Berdych double-faulted twice and missed a game point before the now rampant Murray stepped out wide and hammered a forehand down the line on break point.
An ace sealed the set, and left Berdych having won just three games in 75 minutes of tennis.
The fourth set came to life in game six when a fired-up Murray saved a break point with a brilliant cross-court forehand, and another with a serve, receiving a time warning along the way before smacking the ball high in delight at holding on.
Both men were pushing hard for the break, and taking every opportunity to stare the other down, but it was Berdych whose nerve failed him.
Two errors and a double fault handed Murray break points at 5-5 and the Czech sent a third groundstroke flying long, allowing the Briton to serve it out with an ace moments later.