Thirty years ago, the boy from the Gellideg estate challenged Mexican Lupe Pintor for his WBC Bantamweight belt.
Despite defying the odds to dominate the early stages of the fight, he was knocked out in the 12th round, never to regain consciousness again.
In a typically hard-fought battle for life, he survived for another two months, but on 4 November 1980, Johnny Owen eventually succumbed to his terrible head injuries.
Born to a large Merthyr family, Johnny soon learned to stick up for himself, and started his interest in boxing aged just eight.
He was to remain in the amateur sport until he was 20, an unusually long time by modern standards; winning 106 of his 124 bouts.
He fought for Wales 17 times, and was victorious on 15 occasions.
Yet despite this impressive record, Merthyr boxing writer and professional referee, Winford Jones, says that Johnny's true talent didn't lie in the shorter format of the sport.
"Johnny was a machine. His great skill wasn't his strength - though he never took a backwards step and could punch as hard as anyone of his weight - it was his stamina.
"He could fight for hours, and would wear opponents down by outlasting them.  You could see this talent far more in 12 and 15-round professional fights, than you could in the three rounds allowed in amateur boxing."
His professional career lasted just four years, from 1976 to 1980, but in that time Johnny Owen crammed in 28 fights; winning 25, drawing one and losing two.
Though in a sense it is possible to argue that he never lost fair and square.
His first defeat came against Spain's Juan Francisco Rodriguez, in a fight for the European belt.
In what's now widely regarded by experts to have been a travesty of a home-town decision, the judges awarded Rodriguez a fight which Owen had clearly bossed.
His second, and final defeat came in the fatal clash with Pintor, a  fight in which he at least held his own, and may have won, were it not for the head injuries which he'd sustained.
But at one stage Owen's record read 22-0, winning his first fight against a former Welsh champion, George Sutton.
In his sixth fight he again saw off Sutton to claim the Welsh title.
By bout nine he had the British belt, beating Paddy Maguire, and in November 1978 he became the Commonwealth champion, stopping Italian-Australian Paul Ferreri.
Owen wasted no time in avenging the controversial defeat to Rodriguez in the spring of 1979.
Just a year later he convincingly bettered him in a re-match in Ebbw Vale, setting up his World title chance against Pintor.
Winford Jones was lucky enough to referee some of those early fights.
"In what I think must have been his fourth or fifth fight, I remember he was taking on an Irish lad, and I had to stop it in the fourth round because Johnny was murdering him.
"It makes you think about what happened a few years later on to Johnny.
"But he was fearless, you could tell, even then, that he had the makings of a champion, and sadly the potential to get hurt, because he would never give in, and never take a backward step in a fight."
Yet the man who was so fearless in the ring, was the shyest and most awkward of characters in the glare of the media.
Professional life
Inconceivable in modern boxing, Owen would simply shake hands with his opponent at a weigh-in, avoiding confrontation, and usually conversation of any kind.
He declined requests for all but a tiny handful of interviews.  Perhaps boxing journalist Hugh McIlvanney summed it up best, when he wrote: "The tragedy of Johnny Owen was that he was only articulate in the most deadly of languages."
When Owen was knocked down in the ninth round of the WBC title-challenge in Los Angeles, it was the first time he'd been on the canvas in his professional life.
But he was to go down twice more in the 12th round, never getting up from the second.
The legacy of Johnny Owen lives on in Merthyr.
After he died, a Â£100,000 relief fund raised for his care, went instead, according to his family's wishes, to establish a special-care baby unit at the town's Prince Charles Hospital.
Important safety lessons were learned, when it became evident from his post mortum, that Johnny had been born with a critical weakness of his skull.
Whilst boxing will never be entirely safe, the routine scans introduced following Johnny's death, have undoubtedly saved many other lives.
Rather than bitterness, his family extended a hand of friendship and solidarity in boxing to Lupe Pintor, telegraphing him shortly after Johnny's death, to urge him not to feel guilty, and to continue boxing.
Mutual respect
In 2002, on the 22nd anniversary of Owen's death, his father Dick unveiled a statue of his son in Merthyr, arm-in-arm with Pintor.
Winford Jones said was it was one of the most moving experiences of his life.
"Before the unveiling, I asked Lupe, in my scratchy Spanish, how he was finding the day, and he replied 'Very awkward'.
"But he'd come nevertheless, and the people of Merthyr gave him a tremendous reception.  I think that speaks volumes for Merthyr, and in particular for Lupe and Dick."
"I cried when I saw them hug in front of Johnny's statue.
"That is an image that all boxers should be shown before they set a toe in a ring, as it encapsulated the honour and mutual respect that should always be present in the sport."
In the firmament of Welsh boxing legends, no star has burned so brightly, or for such a tragically short time, as the "Merthyr Matchstick", Johnny Owen.