The former heavyweight champion moved cautiously for most of the round before unleashing his right hand which has long been considered the best in the business.

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Wilder knew it was over, posing against the ropes even before the fight had been stopped.

The Bronze Bomber 43-2-1 (42 KOs) won emphatically in his first fight since getting stopped twice by Fury, the latter in the 11th round last October after Fury got up from two knockdowns.

But Helenius (31-4) wasn't getting up from the straight right hand that ended the match with three seconds remaining in the first round at Barclays Centre in Brooklyn.

He used his roughly 40-pound edge to move Wilder back for much of the round and had him back in the corner when Wilder unleashed the right that ended the Finnish fighter's hopes of moving closer to a title shot.

"When you fight Deontay Wilder, you have to have your A-plus-plus game," Wilder said.

"I set him up. I allowed him to reach and when he reached, I attacked. It was a great fight."

Wilder could quickly get another one for the heavyweight title after showing again why his power makes him one of the can't-miss attractions in the sport.

He held a portion of the heavyweight title for five years and could seek a chance against Oleksandr Usyk, who owns the three belts besides the one Fury took from Wilder. Other names that will be mentioned include former champions Anthony Joshua and Andy Ruiz Jr.

"I have been hearing rumours about Usyk, but he's not here, is he?" he added.

"When guys see these knockouts, they turn the corner away from me. So, I'm down for whatever, whether it's Andy Ruiz or Usyk, let's bring it on.

"Deontay is back and the excitement in the heavyweight division is back."