Flyweight world champion Roman “Chocolatito” Gonzalez, one of the top pound-for-pound fighters in the world, will make his third title defense when he faces former unified titleholder Brian Viloria on Oct. 17 in one of the best fights that could be made in boxing’s smaller weight divisions.

The fight, rumored for weeks but formally announced on Tuesday by K2 Promotions and Teiken Promotions, will take place at Madison Square Garden in New York in the co-feature on the HBO PPV-televised undercard of the middleweight title unification bout between Gennady Golovkin (33-0, 30 KO) and David Lemieux (34-2, 31 KOs).

“I know Brian Viloria is a great [former] champion and it will be a hard fight, but I am ready for the challenge,” Gonzalez said. “I have faith that God will give me the strength to keep training and be able to give all my fans my best fight ever.”

The 28-year-old Gonzalez (43-0, 37 KOs), a former junior flyweight and strawweight champion before vacating those titles to move up in weight, was a big hit in his last fight when he made his HBO debut — his first wide American television exposure — on May 16 at the Forum in Inglewood, California. He violently blew away former junior flyweight titlist Edgar Sosa in the second round on the undercard of Golovkin’s title defense against Willie Monroe.

The promoters and HBO liked the pairing of Golovkin and Gonzalez, both exciting punchers, and wanted to do it again.

“We’re thrilled to welcome back Roman Gonzalez as the co-feature once again to one of Gennady’s fights,” K2 Promotions managing director Tom Loeffler said. “His performance at the Forum in May was extraordinary and made for a terrific pairing. With Roman defending his title against former world champion Brian Viloria, one of the best flyweights in the world, fans in the arena and those watching on HBO pay-per-view will see an outstanding battle as the lead-in to Golovkin versus Lemieux.”

Gonzalez, of Nicaragua, is regarded as the best fighter in the nation’s history behind only the late, great Hall of Famer Alexis Arguello, who discovered Gonzalez, mentored him and trained him early in his career.

Known as “The Hawaiian Punch,” Viloria (36-4, 22 KOs), a 2000 U.S. Olympian and former flyweight and junior flyweight titleholder, is still going strong at age 34.

He knocked out Hernan “Tyson” Marquez in the 10th round to unify to flyweight world titles in November 2012 before losing them by split decision to Juan Francisco Estrada in March 2013 in Macau, China.

Since then, Viloria has won four fights in a row — including a first-round knockout of Omar Soto on July 25 — and his promoter, Top Rank, promised him another title shot.

“I’ve fought and won on the world’s biggest stages against the best of the best. I’ve prepared my whole life to win at every level of competition from world amateur titles to the Olympic Games to professional world titles,” Viloria said. “And this fight against Roman Gonzalez is likely to be my biggest challenge yet. But it’s Roman’s biggest challenge too. This is the realization of my dreams and I will make the most of it on fight night.

“I applaud Roman for accepting this fight. Together we will give boxing fans something special — something they can talk about for a very long time.”

Viloria was one of three fighters in contention to get the title shot against Gonzalez. The others were former junior flyweight champion Giovani Segura (32-4-1, 28 KOs), of Mexico, and Puerto Rican contender McWilliams Arroyo (16-2, 14 KOs).

The addition of Gonzalez-Viloria to the card gives it a strong 1-2 punch with the much-anticipated main event.

“On Oct. 17th, fight fans are going to be treated to a tremendous night of action headlined by not only the spectacular Golovkin-Lemieux main event, but also a terrific co-feature starring Chocolatito Gonzalez and Brian Viloria,” said HBO Sports senior vice president Mark Taffet, who runs HBO PPV. “Chocolatito was spectacular in his HBO debut last May and Brian is the essence of an intense competitor. The co-promoters of this event are determined to deliver tremendous value to boxing fans on Oct. 17 at Madison Square Garden.”

One of the other bouts in the works for the pay-per-view portion of the card is a heavyweight fight between Cuban puncher Luis “King Kong” Ortiz (22-0, 19 KOs) and former world titleholder Bermane Stiverne (24-2-1, 21 KOs), who would be fighting for the first time since losing a unanimous decision and his title to Deontay Wilder on Jan. 17. The fight has been agreed to but the contracts have not yet been signed.