Feliciano Lopez became the first wildcard to win the Queen’s singles title since Pete Sampras in 1999 by beating fellow veteran Gilles Simon.
Lopez, who won the 2017 title, triumphed 6-2 6-7 (4-7) 7-6 (7-2).
The Spaniard had spent almost five hours on court on Saturday and France’s Simon, 34, had come through some long matches – and this was another slog.
Lopez, 37, returns to the court later in the doubles final alongside Andy Murray at the Fever-Tree Championships.
The Scot is playing his first tournament since having hip surgery in January and the pair will meet Joe Salisbury, another Briton, and American Rajeev Ram for the trophy.
For Lopez, lifting the Queen’s trophy again has capped an extraordinary week at the west London club.
Now ranked 113th in the world, he had won just three singles matches this year going into the tournament.
The victory – over former world number six Simon, who had also spent more than 10 hours on court in the singles going into the final – was Lopez’s eighth at Queen’s this week across the singles and doubles.
A ninth, alongside Murray, will make him the first man to lift both trophies at Queen’s since Pete Sampras in 1995.
“I don’t know how I did that,” the Spaniard said.
“I thought the best moment of my career was when I held this trophy in 2017 but it’s not. It’s right now.”
‘Now my girlfriend knows I’m a decent tennis player!’
The two players, with a combined age of 71, initially showed little movement and variation as they became locked in a baseline battle.
Lopez’s strong service game proved the difference in the first set and he broke in the first and fifth games – and held off three break points in the sixth – on his way to the opener.
Simon broke at the first attempt in the second set for a 2-0 lead, only to see that wiped out instantly by the Spanish left-hander.
The pair easily traded holds on the way to the tie-break, although Lopez did plant a straightforward volley into the net for 30-30 at 5-5, which would have given him a glimpse of an opportunity.
Lopez recovered to lead 3-1 and 4-2 in the breaker but then missed another volley for a 5-3 lead as Simon battled back to win and force a decider.
That was also an attritional set as Simon, bidding to become the first Frenchman to win the singles at Queen’s, kept finding passing winners when Lopez came forward.
Lopez eventually forced his first match point at 6-5 after a lengthy deuce, sending a tired forehand into the net.
In the deciding tie-break, Lopez moved 5-2 ahead with a stunning volley which left him screaming with delight, then pulled out a service ace out wide for four more match points.
He took the first when, after charging forward to the net again, Simon could only tap a forehand into the net.
Lopez ripped off his bandana after clinching victory, looking over to the stands where his fiancee Sandra Gago – who he is set to marry in September – was crying in celebration.
“When we met, things weren’t going too well and I kept losing,” Lopez, whose previous tour win was the 2017 Queen’s title, told the crowd. “Now she can see I’m a decent tennis player!
“I’m so happy for you; we can share this together.”