The 25-year-old Mexican dropped Khan with a straight right hand over a left jab that sent the Briton crumbling to the canvas where he lay there motionless for a couple of minutes.
Khan eventually got up and went to his corner as the savage end, to what was supposed to be the biggest fight of his career, will undoubtedly strengthen the notion that he has a soft chin.
It was a shocking end to what had been a surprisingly close fight up to that point as Khan moved up two weight classes to face the bigger champ.
WATCH: Amir Khan knocked out by ‘Canelo’
The 29-year-old Khan started strong and even won the first couple of rounds before Alvarez worked his way into the fight at the brand new T-Mobile Arena.
Alvarez is now mandated by the WBC to fight unbeaten two-belt champ Gennady Golovkin, who was at ringside Saturday.
At Friday’s weigh-in, both boxers scaled 155 pounds, bang on the catch-weight limit.
Many Mexicans were in Las Vegas to celebrate the Cinco de Mayo festival weekend, meaning the majority of the crowd was on Alvarez’s side.
There was also a vocal contingent of Khan‘s fans, who made the trip from Britain for the title fight.
Also in attendance at ringside for the fight were boxing legends Evander Holyfield, Roberto Duran and Roy Jones as well as the fight promoter Oscar de la Hoya.
Alvarez-Khan was the first boxing match to take place at the 20,000-capacity T-Mobile Arena. The $375 million facility opened last month.
After the fight, WBC President Mauricio Sulaiman had a conversation with Khan. He told: “I was telling him [Khan] I was proud of him but he was really disappointed because he really wanted to win. I’m relieved he is ok though.”
Khan said: “It’s time Canelo took the risk and fought Triple G. I showed my balls by stepping up against Canelo a both guy. This is boxing. I found it hard to turn down the challenge. My natural weight is welterweight.”
GLIMPSES OF THE FIGHT:
Picture courtesy: The Mirror