Australia's Jason Day held his nerve to end five years of close calls at the majors with an emotional breakthrough victory by three shots over American Jordan Spieth at the PGA Championship.
World number five Day, two ahead of Spieth overnight, never relinquished his lead as he closed with a five-under-par 67 on a blustery afternoon of hazy sunshine at Whistling Straits to post a major record low of 20-under 268.
The previous best at a major was the 19-under total of 269 recorded by Tiger Woods when he triumphed by eight shots in the 2000 Open at St Andrews.
Day fended off the challenge of Spieth, who had been bidding for a rare third major victory in the same year, with four birdies in the first seven holes, followed by three more after the turn.
The 27-year-old Australian, who had previously recorded nine top-10 finishes in the majors, six of them in the top four, had to wipe tears from his eyes before he tapped in a par putt from just one feet on the 18th green.
Spieth, the Masters and US Open champion, had to settle for second after closing with a 68, a finish that secures him the number one ranking for the first time at the expense of Rory McIlroy.
Day, who was embraced by his pregnant wife Ellie as he made his way off the green, became the fifth Australian to win the PGA Championship after Steve Elkington (1995), Wayne Grady (1990), David Graham (1979) and Jim Ferrier (1947).
"It's an amazing feeling," a visibly emotional Day told CBS Sports after being presented with the coveted Wanamaker Trophy, which he hoisted high in celebration.
"Winning the PGA Championship is very special."
Fittingly, the first person to embrace him was his caddie and mentor Colin Swatton.
Day first met Swatton when, following the death of his father, his mother borrowed enough money to send him to the same international boarding school at Kooralbyn attended by former world number one Adam Scott and Australian athletics star Cathy Freeman.
Their initial interaction resulted in an argument when Swatton, who was the golf coach, wanted Day to work on his short game. Day preferred to play the par-three course but, after reflecting on the sacrifices his mother had made, apologised to Swatton in front of the other pupils.
"It's been a long-time relationship between me and Colin," Day said after a record 20-under-par total at Whistling Straits gave him a three-shot win over new world number one Jordan Spieth.
"For him to be on the bag, not only for my first win on the PGA Tour but my first major championship win, I mean he's taken me from a kid that was getting in fights at home and getting drunk at 12 and not heading in the right direction to a major champion winner. And there's not many coaches that can say that in many sports.
"If my dad didn't pass away [from cancer], I don't think I would have been in a good spot. Where I was based, I mean it wasn't the greatest place. Who knows where I would have been? I honestly don't know.
"That's why a lot of emotion came out on 18, just knowing that my mom took a second mortgage out on the house, borrowed money from my aunt and uncle, just to get me away from where I was to go to school, seven hours drive.
"I remember growing up, we were poor. I remember watching her cut the lawn with a knife because we couldn't afford to fix the lawn mower. I remember not having a hot water tank, so we had to use a kettle for hot showers. We would put the kettle on and go have a shower, and then my mom would come bring three or four kettles in, just to heat them up. And it would take five, 10 minutes for every kettle to heat up.
"So just to be able to sit in front of you guys today and think about those stories, it gets me emotional knowing that I'm the PGA Champion now and it feels good."
South African Branden Grace, who pulled within a shot of Day's lead after making four birdies in five holes from the third, signed off with a 69 to place third at 15 under.
Day made a confident start to the final round when he stretched his lead to three after getting up and down from a bunker to birdie the par-five second, before picking up further shots at the fifth and sixth.
Though Spieth also birdied five and six to remain two behind, Day drained a monster 50-footer to birdie the par-three seventh, shouting out "Yes" in celebration after his ball disappeared into the cup.
Though the Australian bogeyed the eighth, after his tee shot ended in a poor lie in a bunker, he did well to salvage par at the ninth when he chunked a wedge approach from the middle of the fairway, chipped to nine feet and sank the putt.
Two ahead at the turn, Day picked up further shots at the 11th and 14th to move four strokes clear and could afford the luxury of a bogey on 15 before finishing birdie-par-par.
McIlroy, back in action this week to defend his PGA Championship crown after being sidelined with an ankle injury, signed off with a 69 to finish at nine under.
