Roger Federer beat fellow Swiss Stan Wawrinka 7-5 6-3 1-6 4-6 6-3 to reach the Australian Open final and stay on course for an 18th Grand Slam title.
The 35-year-old will face Rafael Nadal on Sunday if the Spaniard beats Grigor Dimitrov in Friday's semi-final.
The Swiss, returning from a six-month lay-off to rest his left knee, last won a major at Wimbledon in 2012.
He is the oldest man to reach a Grand Slam final since Ken Rosewall did so at the 1974 US Open at the age of 39.
"I couldn't be happier right now," said Federer.