Haney, 23, is the first boxer to unify the belts at lightweight since Pernell Whitaker in 1992, and the first to do so under the era of four belts (WBC, WBA, IBF and WBO) which began in 2004 .
Kambosos fell victim to Haney's sensational speed, instinct and relentless left-handed straight.
Frustrated, the Aussie struggled to land enough big punches.
The American also performed a real defensive tour de force.
His skill and his tactical sense won against 41,000 spectators almost all won over to his opponent, in a white-hot Marvel Stadium in Mebourne.
All three judges gave scores in favor of Haney (116-112, 116-112 and 118-110).
"It's a dream come true," Haney said.
The American had received a big boost the day before the fight when his father and trainer, Bill, obtained a visa at the last minute after being refused entry to Australia because of an old doping conviction. about thirty years old.
"I felt comfortable," continued Haney, undefeated in 28 fights (15 of them by knockout).
"I stuck to the game plan... I deprived him of what he does best."
Kambosos, 28, meanwhile suffers his first professional defeat in 21 fights since his debut in 2013.
With his victory, Haney enters a very exclusive club of boxers, since he is only the eighth in history to unify the belts.
The other seven are Bernard Hopkins (middleweight), Jermain Taylor (middleweight), Terence Crawford (super lightweight), Oleksandr Usyk (middleweight), Josh Taylor (super lightweight), Saul Alvarez (super middleweight) and Jermell Charlo (super welterweight) .
© 2022 AFP