Manny Pacquiao will be the man to bring an end to Floyd Mayweather Jr's perfect 47-0 record, according to former world heavyweight champion George Foreman.

The pair go head-to-head at Las Vegas' MGM Grand on May 2, in what is expected to be the largest-grossing fight in the history of the sport.

Many have Mayweather as favourite to defeat Pacquiao on perceived home turf, but Foreman is backing the Filipino to prevail.

"I think Pacquiao to win six rounds, the seventh will be kind of even. Mayweather will come on in the last rounds but it will be too late. The fight will be won by a single round," he said.

"Mayweather starts off early looking for a rhythm, Pacquiao will pop him early on, he will tire and Mayweather will come on in the later rounds but he will lose.

"It's going to be a fantastic, amazing boxing match. It will live up to all the hype, it really will."

Foreman himself was 40-0 until he lost to Muhammad Ali in the famous Rumble in the Jungle in 1974, and it took him over a year to return to the ring after that defeat.

"I'm the one guy who knows what it's like to be undefeated going into a fight like that and to be knocked off that pedestal," Foreman said.

"Pacquiao has it a little better. He is already picked as the underdog. There's not a whole lot of pressure on him.

"But when you have never lost before in a fight of this magnitude, there's so much pressure on you, more pressure than you have ever had before, more pressure than on any other athlete right now.

"You lose your perspective on who you are as a human being. This could devastate him [Mayweather] as a boxer, not as a man but as a boxer. He might have to go out in the country somewhere if he lost."