Wawrinka fought back strongly after being outplayed in the first two sets, but Federer held on to win 7-5, 6-3, 1-6, 4-6, 6-3 and reach his 28th Grand Slam final.
The first set followed serve as the Swiss compatriots traded blows with quality and power—Wawrinka saved three break points to make it 2-2, while Federer had to save two in the following game.
The pair produced a fascinating duel. Federer used every shot in his arsenal to try to prevent Wawrinka from getting into his rhythm, and Wawrinka responded with some typically robust efforts and outstanding serves.
Christopher Clarey of the New York Times praised both players—Federer for his exquisite backhand, Wawrinka for his speed and movement across the court:
Former British No. 1 Andrew Castle was also enjoying the display:
The set looked to be heading to an inevitable tiebreaker when a correct challenge from Federer handed him a set point after Wawrinka fired a backhand wide.
The No. 17 seed then finally drew first blood when Wawrinka netted a forehand at the crucial time.
Federer turned the screw in the second set as he took control with a break, wearing down the No. 4 seed over the course of a rally until Wawrinka eventually succumbed with a backhand into the net.
Wawrinka was visibly frustrated—which he vented on his racket to receive a code violation—while Federer was the epitome of composure. The latter was soon just one set away from the final as he placed his shots with unerring accuracy.
The 2014 Australian Open champion benefited from a medical break ahead of the third set, however, and returned to court with renewed focus and power.
Indeed, that was evident as he broke his opponent twice in succession—courtesy of a superb backhand and an error from Federer—to race back into the contest.
Ben Rothenberg of the New York Times noted how quickly the momentum changed:
Wawrinka continued in that vein at the start of the fourth, as he broke Federer for the third time in a row with a backhand pass.
Federer was able to stop the rot, though, as he hit back immediately, working his way to deuce before a double-fault and an error from Wawrinka made it 1-1.
A deft right-to-left forehand helped the 31-year-old grab a second break to head 5-4 up, and he served out the set to love—his first service game to love in the match. The Australian Open's official Twitter feed captured the moment:
Federer twice showed tremendous resilience to save a break point and hold in back-to-back service games early in the decider, and Wawrinka paid for his profligacy when he double-faulted to hand his opponent a break and a 4-2 lead.
The pendulum had swung at that point. While he served to stay in the tie valiantly, there was little Wawrinka could do to prevent Federer from seeing out the match.
Per BBC Sport's Jonathan Jurejko, Federer was ecstatic to have won: "I don't know how many break points I saved, it was tough. I felt Stan had the upper hand from the baseline in the fifth set. I just knew I had to stay in it somehow and play aggressive."
He continued: "I feel like he gave me a bit of a cheap break, but after that I served it home, and I couldn't be happier right now. I felt like everything happened so quickly at the end, I had to check the score at the end. It feels amazing. I never ever in my wildest dreams thought I'd come this far in Australia. It's beautiful, I'm so happy."
Federer's victory keeps alive the possibility of a romantic final with Rafael Nadal—he will play the winner of the Spaniard's semi-final with Grigor Dimitrov, to be played on Friday.
Should Federer win, he would extend his record to 18 Grand Slam singles titles.