He died of heart failure, according to the NHK.
Inoki was 1.9 m tall and pioneer of mixed martial arts in Japan. He was crowned world heavyweight champion Muhammad Ali in a zany wrestler-versus-boxer bout in Tokyo in 1976.
He was elected the upper house lawmaker for the now-defunct Sports and Peace Party in 1989.
He travelled to Iraq before the Gulf War in 1990 to gain the release of Japanese hostages.
In 1995, Inoki lost his seat and retired as a wrestler in 1998, but was re-elected to the upper house in 2013 as a member of another opposition party.
Inoki travelled to dozens of times to help resolve the issue of Pyongyang's abduction of Japanese citizens during the Cold War, before ending his political career in 2019 after having built a strong personal connection with North Korea over the years.
The wrestler - whose birth name was Kanji Inoki - said he wanted to contribute to world peace through sports and had arranged martial arts and wrestling festivals in North Korea, often meeting high-ranking officials during his visits.
Asked about them at the time, the then Chief Cabinet Secretary Yoshihide Suga reminded journalists that Tokyo had a travel ban on North Korea, urging the politician to act appropriately. Japanese television news provided blanket coverage of Inoki's trip, and the visits continued to draw interest, given the lack of details about life in North Korea.
Inoki, unmistakable from his outsized chin and trademark tie and red scarf - even in summer - forced the government to take an official position on aliens when he presented a question to a budgetary committee in 2017 saying he had seen a mysterious flying object disappearing over the horizon.
In 2020, Inoki said he had been diagnosed with heart disease.