Francisco Cerundolo was crowned Queen's champion after beating Tommy Paul 6-7 (4-7) 6-4 6-3 in the longest final in championship history at three hours and three minutes.
Paul, the 2024 champion who was on a nine-match winning streak in the tournament having missed last year's edition through injury, battled back from 3-5 down to win a tie-break 7-4 in a 66-minute first set.
Cerundolo, though, responded by fighting off a vital break point at 4-4 to then break himself and force a decider.
The No 8 seed then seized the momentum to surge 5-2 ahead in the third set, but squandered three match points against the serve as Paul fought to stay in the match.
Cerundolo was able to keep his cool under pressure and serve out the match for his fifth singles title - and undoubtedly the biggest of his career - in an grass-court epic ahead of Wimbledon.
"I want to thank my mum and dad - they only arrived for the last two games!" Cerundolo said after his victory. "It's the first time my father has taken a plane to watch me play outside of Argentina.
"I felt really privileged here this week - you make me feel at home. Thank you for coming out and supporting me throughout this week."
Katie Boulter saw her Bad Homburg Open campaign end with a 7-6 (7-5) 3-6 3-6 defeat to Layla Fernandez in the first round.
The British No 2 leapt out to an impressive first-set lead against Fernandez, notching five aces on her way to a tie-break victory against the world No 22.
The Canadian, though, got her revenge after Boulter beat Fernandez on her way to the Queen's semi-final just over a week ago, coming back from a set down impressively in a three-hour and 12-minute epic in Germany.
Boulter opted out of Eastbourne to play in the German tournament, but her early exit now means she is not scheduled to play any matches before she enters Wimbledon.
Former Wimbledon boys' singles champion Henry Searle captured the biggest title of his career so far at the Dublin Challenger.
The 20-year-old Briton continued the impressive form he had shown all week, defeating world No 152 Jurij Rodionov 6-4 6-2 in the final.
Searle has a wild card into Wimbledon singles qualifying and will also team up with mentor Dan Evans in the men's doubles main draw. This will be the former British No 1's final professional tournament.
"I'm excited for it," he said. "I just need to get back, practise a little, recover, and I should be ready to go on Monday."
Searle has won two other ITF $15k tournaments this year, but his title in Dublin is by far the biggest of his career to date. He is currently set to jump 91 places in the live ATP rankings to a new career-high of world No 263.
Oliver Tarvet's last memory of Wimbledon is taking on Carlos Alcaraz on Centre Court, but he is more than happy to do things the hard way again.
The Briton's run through qualifying to the second round as a 21-year-old ranked 733 was one of the stories of the tournament 12 months ago - not least because, as a university student in the United States, he was not allowed to keep his £99,000 prize money.
Having graduated from the University of San Diego last month following a stellar college career on court, Tarvet will have no such problems with whatever earnings he collects this time around.
And that will be at least £20,000 - the remuneration for players losing in the first round of qualifying, for that is the path he must take again, having been overlooked for a main-draw wild card.
Had this not been such a competitive year, Tarvet might well have been given a shot in the men's singles, but he has no complaints.
"I feel like it's not something you can expect to get, any wild cards into a Grand Slam," he said. "I'm more than delighted with any opportunity."
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