"I feel like the happiest person in the world. How could I have come so far at the world's oldest age of 80," Miura said. "I have never felt like this in my life. But I've never been more exhausted than this."
"I can see the scenery of the Himalayas below me. I really thank every one of you for your support."
It was his third conquest of the 8,848-metre (29,028-foot) peak, and his latest feat means he recaptures the record he previously held for being the oldest person to climb Everest.
He previously reached the summit when he was 70 and 75.
His 2003 record was broken in 2007 when fellow Japanese Katsusuke Yanagisawa scaled the summit when he was 71 years old.
Miura conquered Everest for the second time in May 2008, just one day after Nepal's Min Bahadur Sherchan made it to the top at the age of 76.
Until Thursday morning, the Nepalese had been the world record holder, according to Guinness World Records.
Miura was now climbing back down the mountain, a Nepalese tourism official said, confirming the successful ascent.
"He reached the summit this morning and is currently descending to camp four," the official, Gyanendra Shrestha, told AFP from Everest Base Camp.
Veteran adventurer Miura came to worldwide attention in 1970 when he became the first person to ski down Everest.
His parachute-aided descent was documented in the 1975 film "The Man Who Skied Down Everest" which won an Academy Award for Best Documentary.
High-octane endeavours are in his blood -- his father Keizo skied down Mont Blanc at age 99.
More than 3,000 people have successfully scaled Everest, but the mountain claims lives regularly, with even the best climbers falling victim to its fickle weather.