'Pac Man' has been sidelined since his knockout defeat to Juan Manuel Marquez last December, but he will be back in action against Rios on November 24.
Rios is also coming off a defeat to Mike Alvarado but has been handed a huge clash with Pacquiao that will take place at the Venetian Resort Hotel in Macau, China.
Both fighters have signed terms for the welterweight bout, which will be shown on HBO pay-per-view in the United States.
Pacquiao's long-time trainer Freddie Roach believes that the Filipino star will be back to his best against Rios.
He told ESPN: "Manny is definitely going to get his mojo back with this fight. Brandon Rios likes to fight in the pocket and exchange, and Manny is very good in the pocket too.
"I think it'll be an exciting fight but that Manny is going to land in the pocket at some point and knock this guy out somewhere along the way.
"Rios likes to exchange and his style is not really difficult to figure out, so Manny's gonna hit him."
Pacquaio has lost his last two bouts and is without a victory since 2011.