Confirming the news in a media statement, Millbrook operations director Brian Howie said the resort had been "extremely fortunate'' to have benefitted from Mr Ishii's long-term commitment to Millbrook and Central Otago.
Mr Ishii and his family have owned Millbrook since 1987.
Mr Howie said Millbrook went from strength to strength under Mr Ishii's leadership, hosting Commonwealth heads of government, United States presidents, and members of the British royal family.
"We are devastated to hear news of his passing but are forever grateful for his strong strategic vision and support over the years, which has enabled us to focus on delivering consistent excellence to our guests and members.
"Our thoughts today are with his wife Mrs Hiroko Ishii, daughter Yuki and son Gota and wider family.''
In 2015 Mr Ishii was presented with the Keys to Arrowtown in recognition of his support and contributions to the local community.
In 2016 he was made an Honorary Member of the New Zealand Order of Merit in recognition of his services to New Zealand-Japanese relations, golf and tourism.
