Akebono, a Hawaiian who was the first foreign-born sumo wrestler to become a grand champion, has died aged 54, US officials and Japanese media said Thursday.

Born Chad Rowan in 1969, Akebono was among the most successful sumo wrestlers of the 1990s.

He reached the sport's highest rank of yokozuna, or grand champion, in 1993 and became a Japanese citizen in 1996.

Akebono won 11 tournaments before retiring as a wrestler in 2001 to train younger fighters.

He died in early April after heart failure, Kyodo News agency said.

United States Ambassador Rahm Emanuel called Akebono "a proud Hawaiian and a bridge between the United States and Japan".

"When Akebono became the first-ever foreign-born grand champion, sumo's highest rank, in 1993, he opened the door for other foreign wrestlers to find success in the sport," Emanuel said in a statement.

"Throughout his 35 years in Japan, Akebono strengthened the cultural ties between the United States and his adopted homeland by uniting us all through sport."

Standing more than two metres (6ft 5ins) and weighing over 230 kilos (510 pounds), Akebono was initially considered too tall for sumo but was allowed to join a stable run by Takamiyama, a former wrestler also from Hawaii.

Akebono made his debut in 1988 and rose through the ranks, winning his first top-level tournament four years later.

He gained promotion to grand champion and gained fame for his fierce rivalry with brothers and local favourites Takanohana and Wakanohana, who were born to an elite sumo family.

There have since been six other foreign-born yokozuna, five Mongolians and one other American.

Sumo journalist Shoko Sato knew Akebono for over 30 years and said that the wrestler had felt a heavy responsibility as the first foreign-born grand champion.

"He felt he had to work harder than the Japanese grand champions and had to be recognised as being more Japanese than the Japanese themselves," she told AFP.

"He was only in his 20s at the time and it was a lot of pressure, so sometimes he would overdo it when he went out at night."

Such was his fame, Akebono featured prominently at the opening ceremony of the 1998 Nagano Winter Olympics.

"We would like to express our deepest condolences upon hearing of his passing," said a social media post on X by the official Japanese-language account of the Olympics.

After retiring from sumo Akebono launched a mixed martial arts career, fighting American Bob Sapp in front of a crowd of 45,000 in Nagoya.

He also had a stint in professional wrestling.

US Forces Japan paid tribute to Akebono in a post on X, formerly Twitter.

"We join all sumo fans today in expressing our heartfelt condolences on the passing of former sumo grand champion Akebono," it said.

"A true champion and barrier breaker for becoming the first foreign-born grand champion yokozuna."