Pacquiao, now 46, won titles in multiple weight classes during his career. He'll return to the same venue where he suffered a memorable knockout loss to Juan Manuel Marquez in 2012.
The 2012 fight was the fourth and final bout in the intense Pacquiao-Marquez rivalry. The series ended with two wins for Pacquiao, one for Marquez, and one draw. Their last meeting saw Marquez knock out Pacquiao in the sixth round, a moment many consider one of boxing's best knockouts.
Pacquiao doesn't like to talk much about that fight. When he does, he downplays its significance.
"He was lucky. I was about to finish him in that round... I got careless and he gave me a lucky punch,"Pacquiao once said about the loss.
Marquez sees it differently. He claims the knockout was part of his plan, not just luck.
"From the third round I had already sent a warning ... when he feints, he enters,"Marquez explained after the fight.
Marquez retired after that win, which prevented a fifth match between the two rivals.
Now, Pacquiao wants to prove he can still compete at the highest level. He'll try to win the WBC welterweight title from Barrios. The fight's location adds an extra challenge for Pacquiao. He'll have to overcome any lingering doubts from his last appearance at the MGM Grand.
Boxing fans will watch closely to see if Pacquiao can recapture his old form after such a long time away from professional fights.