Unified women's super middleweight world titleholder Claressa Shields is on a mission to win world titles in at least three weight divisions by moving down the scale rather than up.

Shields will drop down to the middleweight division to face unified junior middleweight world titleholder Hanna Gabriels, who will move up one weight class, for a pair of vacant middleweight belts on June 22 (Showtime, 10 p.m. ET/PT) at the Masonic Temple in Detroit, promoter Dmitriy Salita and Showtime announced on Tuesday.

Also on the card, Christina Hammer will defend her two middleweight world title belts against former titlist Tori Nelson. If Shields and Hammer are victorious, they will fight for the undisputed middleweight title this fall on Showtime. Showtime will air extended highlights of Hammer-Nelson.

Already a super middleweight titlist, Claressa Shields, right, will be looking to add several middleweight belts to her résumé when she takes on Hanna Gabriels on June 22 in Motown. AP Photo/Carlos Osorio

"Women's boxing will shine brightly on June 22 in Detroit as the best fight the best," Salita said. "Claressa Shields, in just her sixth fight as a professional, is once again showing her willingness to take on all challenges when she competes for a [third] world title against one of the best female fighters in the sport.

Hanna Gabriels is a long-reigning world champion and a national hero in Costa Rica. This fight and this card, which features four women's world champions battling each other, is the definition of world-class boxing."

Two-time U.S. Olympic gold medalist Shields (5-0, 2 KOs), 23, of Flint, Michigan, stopped Nikki Adler in the fifth round in August to take her women's super middleweight world title, and she also won a vacant belt. Shields made one defense, rolling to a shutout decision against Nelson on Jan. 12 with the plan to drop down to middleweight and eventually junior middleweight to go for titles in those divisions.

Now she has that opportunity to fulfill the first part of her plan against Gabriels (18-1-1, 11 KOs), 35, of Costa Rica, who will be fighting in the United States for the first time.

"I can't wait to get into the ring on June 22," Shields said. "I love the fight against Hanna Gabriels -- champion versus champion, exactly the kind of fight that I want every time to take women's boxing to new heights. I've said one of my goals is to win world championships in three weight divisions. I'm proud to be super middleweight champion, and on June 22 I will add the middleweight championship to my accomplishments. I'm excited to be working with [trainer] John David Jackson for the next step in my career as I look to conquer another division."

Gabriels has won titles at welterweight and junior middleweight and will move up to middleweight for the first time since she fought at 161 pounds in her pro debut in 2007.

"I'm really excited and grateful to have the opportunity to showcase my skills against Claressa Shields on Showtime," Gabriels said. "This will be a great battle of two world champions, a great night for my country, and a great fight for women's boxing. I only know one thing -- the woman in front of me will lose. I take nothing away from Claressa's accomplishments, but on June 22 she is facing a three-time world champion and I will take the '0' in her record and prove I am the best pound-for-pound fighter in the world."

Hammer (22-0, 10 KOs), 27, of Germany, who has also won a super middleweight world title, will make her 11th middleweight title defense when she faces Nelson (17-1-3, 2 KOs), 41, of Ashburn, Virginia.

"I'm glad Christina Hammer will be fighting that night as well. After I beat champion Hanna Gabriels, I want to unify all the middleweight belts against Hammer," Shields said. "I've never been so motivated. This will be a great year for women's boxing. It's our time!"

Hammer has been a dominant middleweight since winning a title in 2010. She unified two belts by unanimous decision against Kali Reis in 2016 and has made two defenses as a unified titleholder.

"I have been training intensively for months for my first fight in the U.S.," Hammer said. "I can't wait to show my skills, desire and hunger to America and prove that I am the middleweight champion of the world. While I have great respect for Tori Nelson, I promise I will defeat her in spectacular fashion on June 22 and send a message to Claressa Shields. It's my time to shine!"