Horn’s last defeat was on points against Ukraine’s Denis Berinchyk at the London Olympics
In the classroom he’s known as Mr Horn. But in the ring, call him "The Hornet".
A relatively unknown physical education (PE) teacher from Australia is weeks away from taking on Manny Pacquiao for boxing’s world welterweight title.
If 29-year-old Jeff Horn – the "fighting schoolteacher" as promoters have dubbed him – can match the reigning champion, his life could change forever.
Who is Jeff Horn?
Eleven years ago, Horn was a self-described nerd from Brisbane who walked into a boxing club to learn self-defence.
He read books, played board games in the library at lunchtime, and was often the victim of bullying.
The only fighter in the family was his grandfather, Ray Horn, who put on exhibition matches in outback Queensland in the 1930s.
His dad, Jeff Horn Sr, is a builder. His mum, Liza Sykstra, works for the St Vincent de Paul Society.
"I got into a few fights at high school," Horn told the BBC. "I didn’t win the majority of those fights either."
Jeff Horn is scheduled to fight Manny Pacquiao on 2 July
But his trainer, Glenn Rushton, told Horn he could become an Australian champion and set about teaching him an unpredictable boxing style – "broken rhythm pressure fighting".
In 2012, Horn made the Olympic boxing quarterfinals while studying for his education degree. He then turned professional.
Working as a substitute teacher, Horns won prize purses sometimes as low as A$2,000 (£1,100, $1,500). Until recently, he taught students at Pallara State School in Brisbane.
But now his full-time job is being the second-best welterweight boxer in the world – behind only Pacquiao.
"I’m a month out from the biggest fight of my life," Horn said, earlier in June.
"I’ve been getting messages from past students wishing me luck."
How big is the fight?
It has taken months of negotiations to bring about what’s been hyped as the "Battle of Brisbane", scheduled for 2 July. An earlier proposed fight between Pacquiao and Britain’s Amir Khan fell through.
The event has, at least temporarily, rekindled Australia’s interest in boxing.
More than 50,000 people are expected to fill Queensland’s Suncorp Stadium, with tickets selling for hundreds of dollars per seat. It will be televised in more than 150 countries, according to Horn’s sports manager Jim Banaghan.
Pacquiao has lost three of his last eight fights but is said to be keen for a knockout
The boxer’s wife and parents have even been pulled into some of the media attention.
"They’re happy for me but they’re nervous as well. They don’t want to see me get hurt," Horn said.
After Pacquiao’s fight with Floyd Mayweather in 2015 became the most lucrative in history, the Australian bout may be regarded as something of a sideshow. Pacquiao may meet Mayweather for an anticipated rematch.
Pacquiao, 38, is also a serving senator in his native Philippines. During a series of promotional news conferences in Australia in April, Pacquiao appeared more interested in his phone than his opponent.
It was a scene to disappoint fans of boxing trash-talk: two clean-cut fighters speaking politely and respectfully about one another.
Pacquiao is the only boxer in history to win world titles in eight weight divisions
"I know what my opponent is feeling right now is hunger," Pacquiao said.
"I’ve been there. I’ve been there in that situation. When I was starting, when I was young, even at night before I went to sleep, I was thinking about the fight."
Does Horn stand a chance?
Whatever the result, the fight will change Horn’s life. Overnight he will become a millionaire. A victory could go down as one of most important in Australian sporting history.
Legendary promoter Bob Arum, who notably worked with Muhammad Ali, said the huge hometown crowd could hand Horn the advantage to stage a monumental upset.
"If his fight with Pacquiao was in Vegas or Madison Square Garden in New York, I wouldn’t give him much of a chance because I think nerves would take over," he told the Courier-Mail newspaper.
"But the fact that Jeff is going to be fighting in front of so many of his countrymen will calm his nerves and I think he will give a great account of himself."
If Horn wins his career-defining fight, Pacquiao will be granted a customary rematch
Australian fighter Anthony Mundine, himself a three-time world champion, said an upset was possible but warns that 38-year-old Pacquiao is still a force to be reckoned with.
"Even though he is at his end and past his prime, I believe he is still a dangerous fighter," he told the Australian Associated Press. "But anything can happen in boxing."
Horn has been training six days a week before the match, visualising the ring surrounded by thousands of screaming fans and sidestepping inside it with Pacquiao.
Superficially, it’s hard to imagine two more different fighters. Pacquiao spent his childhood living in poverty in the Philippines, and entered politics. Horn grew up in relative prosperity in Australia, and became a teacher. Do they have anything in common?
"We’re both nice guys by the sound of it – except in the ring," Horn said.
"We’re going to be throwing leather trying to finish each other off."