London - Roger Federer saved three match points to beat Marin Cilic 6-7 (4/7), 4-6, 6-3, 7-6 (11/9), 6-3 and reach a record-equalling 11th Wimbledon semi-final on Wednesday.
The 34-year-old seven-time champion also claimed a new record for Grand Slam match wins of 307 as he made a 40th semi-final at the majors.
His dramatic triumph was his 84th win at Wimbledon - taking him level with Jimmy Connors - and gave him a semi-final against Canada's Milos Raonic as he continues his pursuit of an 18th Grand Slam title and a record eighth All England Club crown.
In a thrilling Centre Court confrontation, it was Federer's 10th career comeback from two sets down.
It was a tie which saw him save three match points in a titanic fourth set as Federer became the oldest Wimbledon semi-finalist since 39-year-old Ken Rosewall in 1974.
Federer fired 27 aces and 67 winners to avenge his semi-final loss to ninth seed Cilic in the semi-finals of the 2014 US Open.
"Marin is such a wonderful player and I knew I was in so much trouble in the third set and in the fourth," said Federer.
"I wasn't seeing his serves, he had one chance and took it and then I was down 2-0. He was playing very well and reading my serve and I couldn't read his.
"I just tried to stay in the match and hoped for his level to drop and get a bit lucky. That happened and obviously the breaker was crazy.
"My legs and back were there and serving was key, plus mentally this will give me a hell of a boost."
Federer carved out the only break points of the first set in the fifth game, both of which were saved by the giant Croatian.
Serve dominated with the 27-year-old Cilic racing to a 5/0 lead in the tiebreaker and four set points soon after.
Federer saved one but Cilic held his nerve to snatch the opener, leaving the Swiss facing the grim statistic that he'd only taken one point off his opponent's first serve.
His mood would have darkened knowing that he lost a set in which he had not faced a single break point.
Cilic then showed him the way, breaking for a 2-1 lead and saving a break point in the fourth game when Federer dumped a return off a second serve into the net.
Centre Court groaned when sentimental favourite Federer netted another routine backhand volley in the ninth game before two further uncharacteristic errors off the same wing in the 10th helped Cilic to a two sets lead.
With his coach and 2001 champion Goran Ivanisevic looking on, Cilic looked to have Federer on the ropes, forcing the 17-time major champion into saving three break points in the seventh game of the third set.
But Federer grabbed the lifeline when a fifth double fault by Cilic gave him a first break of the contest before the Swiss star unleashed a text-book backhand drive to secure the set in the next game.
The fourth set, lasting just under an hour, veered from one drama to another.
Cilic sent down his 19th and 20th aces of the afternoon to save break points in the fifth game.
Federer then saved match point in the 10th game thanks to Cilic meekly going long on a return and another with his 18th ace in the 12th.
The Swiss squandered two set points in the tiebreaker, the first with a ballooned forehand with the court at his mercy before he saved a third match point when Cilic netted a forehand of his own.
Then it was Federer's turn to feel the pressure as two more set points came and went before Cilic played one loose forehand too many into the net and the semi-final was level.
Federer had the momentum and broke for a 5-3 lead in the decider, racing to a famous victory with back-to-back aces.