The 27-year-old dominated the opening stages of the bout, dropping the two-time former unified heavyweight champion multiple times.
In a dramatic fifth round Dubois was momentarily stunned by two right hands and just as Joshua looked to pile on the pressure, the 34-year-old was caught by successive right hands himself and he was down again, this time unable to beat the count.
“Are you not entertained?” Dubois said to huge cheers at Wembley.
“I’m a gladiator. I am a warrior to the bitter end. I want to reach this sport’s top level and reach my potential.”
In May, Ukraine’s Oleksandr Usyk became boxing’s first four-belt undisputed heavyweight champion when he beat Tyson Fury, simultaneously holding the IBF title and the WBO, WBC, and WBA.
The Ukrainian agreed to a rematch with Fury rather than facing mandatory IBF challenger Dubois.
