Exhausted Wawrinka battles on in Melbourne farewell after five-set epic
In Melbourne as a wildcard, Wawrinka pulled heroically through in four hours and 33 minutes against French qualifier Arthur Gea.
Now ranked 139, he won 4-6, 6-3, 3-6, 7-5, 7-6 (10/3) to become the first player aged 40 or over to reach the men's third round at a Slam since Ken Rosewall at the Australian Open in 1978.
The former Australian Open champion is playing his last season before retiring and faces the American ninth seed Taylor Fritz or Vit Kopriva of the Czech Republic next.
"Exhausted. I am trying to last as long as possible on my last Australian Open," Wawrinka said in his on-court interview.
Addressing the crowd, he said: "You gave me so much energy, I am not young anymore so need extra energy from you.
"It is an amazing feeling. It was a long match. I don't know how I am going to recover," he added.
Wawrinka, who made his debut at Melbourne Park in 2006, fell a set down but fought back and rattled off an ace to win the second set.
Gea, who at 21 is nearly half Wawrinka's age, hit back to win the third set and put the veteran on the back foot once again.
Despite his advanced years the three-time Grand Slam champion Wawrinka somehow found some reserves of energy as the sun went down.
He broke to take the fourth set by the scruff of the neck and they went to a deciding fifth.
In front of a frenzied crowd, Wawrinka broke to start the final set and Gea had both knees strapped as an enthralling match went down to the wire.
There was nothing in it as the battling duo slugged it out to a thrilling finale.
It was the 49th five-set match of Wawrinka's career at Grand Slam events, surpassing Roger Federer for the most of any player in the Open Era.
Wawrinka won the first of his majors at Melbourne in 2014, a season during which he peaked at world number three.
Along with that title, he won the French Open a year later and the US Open in 2016.
The triumphs all came at a time when Federer, Rafael Nadal and Novak Djokovic were dominating men's tennis.
Wawrinka has 16 career ATP titles although the last came in Geneva in 2017.
He won Olympic gold in doubles alongside Federer at Beijing in 2008.