Anthony Joshua knocked out Francis Ngannou in devastating fashion in the second round for a stirring victory in Friday’s heavyweight bout in Saudi Arabia.

Joshua, the British star, knocked down Ngannou in the first round, knocked him down again in the second round and then delivered the knockout punch at 2:38 of the second round.

The knockout blow, a powerful right hand, left Ngannou out cold. Ngannou, the former UFC champion, was down on the canvas for more than a minute and received oxygen, according to the DAZN broadcast.

The victory was the fourth straight for Joshua (28-3) after his back-to-back losses to Oleksandr Usyk of Ukraine.

“For me, I don’t know if I’m coming into my peak,’’ he said. “I’m just pushing day by day.’’

It was a stunning setback for Ngannou, who knocked down Tyson Fury during his pro debut in October and looked impressive in a split-decision loss. But Joshua, the two-time world champion, was in control from the outset Friday.

Joshua, 34, said he was captivated by Ngannou’s bout with Fury.

Recalled Joshua, “When I saw the fight with him and Fury, I was like, ‘Damn, this guy can fight.’ So I said, ‘I need a piece of that.’ “

But after the fight started Friday, Ngannou, the 37-year-old native of Cameroon, spent almost as much time on the canvas as he did on his feet.

“He’s a great champion,’’ Joshua said of Ngannou (0-2) after scoring the 25th knockout of his career. “And this doesn’t take away anything from his capabilities. …He can come back.’’

Round 1: Ngannou opens with a nice left hook. Fighters measuring the situation. Ngannou looks composed. Big right, mostly blocked by Joshua. … Joshua drops Ngannou with a powerful right! Ngannou back on his feet and beats the eight count. Joshua looks ready to pounce, but time runs out. Joshua 10, Ngannou 8.

Round 2: Ngannou not backing away, but looks a little more tentative. Understandably. Joshua lands hard right. Ngannou throw jabs but nothing connecting. Joshua drops Ngannou again! Another big right! Ngannou back on his feet. And down goes Ngannou again! And he’s down for good!

FIGHT’S OVER!

Anthony Joshua wins with a second-round KO.