Known for his extravagant lifestyle, the King rarely visited Auckland and when he did preferred upmarket hotels to the $9 million Epsom residence, known as 'Atalanga', which protesters stopped him from selling.
Tongan media reported that he met Pope Benedict XVI on February 24 in the Vatican in Rome - and gave the Pope a signed picture of himself.
The news of the King's death spread quickly on Twitter early today, and many Tongans paid tribute.
Christinah Lataisia said: "Black and Purple begin to flood the fales in Tonga to mourn the passing away of our King."
Tessi Leila Tolutau said: "I am saddened by the news, our beloved King of Tonga has passed away ... our country has gone thru major losses in the past couple years."
Another resident said: "Sad day for our little Kingdom of Tonga. RIP King George Tupou V."
King Tupou took reign after the death of his father, King Taufa'ahau Tupou IV, in 2006.
In 2008 he marked his coronation with a $3 million, five-day event which was attended by thousands of people, including the Sultan of Brunei and then New Zealand Prime Minister Helen Clark.
Ms Clark also paid tribute to the late monarch on Twitter.
"Sad news for Tonga with the death of King George Tupou V. I attended his coronation in Nuku'alofa in 2008. RIP."
Three days before his coronation, the King announced that he would relinquish most of his power and be guided by his Prime Minister's recommendations on most matters.
Shortly after his coronation, he appointed his younger brother, Prince 'Ulukalala Lavaka Ata, as Crown Prince and heir to the throne.
The Prince was at the King's bedside in Hong Kong when he died.
In September last year, the King received the Grand Cross of the Order of Merit of the Hungarian Republic from Hungarian president Pal Schmitt.
In February he received the Knight Grand Cross of the Royal Order of Francis I from Prince Carlo, Duke of Castro.
His interests were described as being wide and varied and included everything from documentary-making to walking his pet poodle and playing war games with toy-soldiers.
He was also known for wearing a monocle and pith helmets.