Opelka came through 7-5 3-6 4-6 6-4 8-6 against the 22nd seeded Swiss for the biggest win of his career and there will be plenty of bigger names in the draw now scrabbling anxiously for a tape of this match.
"It's a huge win. More so the situation of the match being down two sets to one against him," Opelka told reporters.
"He got really comfortable, started hitting some really good returns. I had to adjust a lot. My mind was always thinking, especially after I lost the third set."
At 6ft 11in (2.10 metres) the former Wimbledon junior champion is the joint-tallest-ever ATP-ranked player (with Ivo Karlovic) and, unsurprisingly, his biggest weapon is his serve. It reached 142mph (228kph) on Wednesday - the fastest of the Championship so far - and, combined with some surprisingly deft court movement, is the perfect Wimbledon weapon.
Wawrinka, who has never gone beyond the quarter-finals at Wimbledon despite winning all three of the other slams and previously reaching number three in the world rankings, could not deal with it at all in the first set.
The 34-year-old eventually used all his experience to work things out and start getting it back and then treating the crowd to some of his sublime backhand winners en route to taking the second and third.
But, just as it seemed as if he would go through smoothly, Opelka found another gear to snatch the fourth.
From then on Wawrinka was having to work harder and harder to hold, while rarely threatening to break. The full match statistics showed the American successful with 73 percent of first serves compared to the 64 percent of Wawrinka and Opelka lifted that to a remarkable 91 percent in the fifth set.
Those figures proved the difference eventually as Wawrinka, at full stretch to even reach, let alone return most of them, was eventually worn down.
"I started holding more easily, I'd had to save so many break points before that," Opelka said of the turnaround. "I made some adjustments and was then able to spend more energy trying to break."
Opelka, who will next face 15th seed Milos Raonic, said that he had "always been a pretty good mover - underrated maybe. Some guys don't expect it when they play me for the first time."
In a period of declining fortunes for American men's tennis, the victory was warmly welcomed former world number four and highly respected coach Brad Gilbert. "Wow, what a clutch performance from big fella Opelka in winning 1st career 5 setter over Stanimal," he tweeted.
Wawrinka had few complaints. "Against those big servers you know you're not going to have a lot of chances and you get under pressure a little bit more," he said.
At the end he went for it. He went bigger than me, more aggressive, and he deserved to win".
(Reporting by Mitch Phillips, Additional reporting by Rohith Nair in Bengaluru; Editing by Alison Williams)
