Japan has formally named its first home-grown sumo grand champion in almost two decades, in a boost to the traditional wrestling sport, BBC reports.

Kisenosato, 30, was promoted to the top-most yokozuna rank after his win in the first tournament of the year.

He is the first Japanese-born wrestler to make it since Wakanohana in 1998. Five wrestlers from American Samoa and Mongolia have made it in the interim.

Foreign wrestlers have come to dominate sumo, amid a lack of local recruits.

Kisenosato, who comes from Ibaraki to the north of Tokyo and weighs 178kg (392 pounds), has been an ozeki - the second-highest rank - since 2012.

After being runner-up on multiple occasions, he finally clinched his first tournament victory - and thereby his promotion to yokozuna - in the first competition of 2017.

"I accept with all humility," Kisenosato said in a press conference after the Japan Sumo Association formally approved him.

"I will devote myself to the role and try not to disgrace the title of yokozuna."