“The Ministry of Presidential Affairs condoles the people of the UAE and the Islamic world on the passing of Sheikh Khalifa bin Zayed Al-Nahyan on Friday, May 13,” the official WAM news agency said.
The ministry has declared 40 days of mourning with flags at half-staff beginning on Friday, with the public and private sectors suspending operations for the first three days.
Sheikh Khalifa became the second president of the UAE in November 2004, succeeding his father as the 16th ruler of Abu Dhabi, the richest emirate in the federation.
Since 2014, when he underwent surgery following a stroke, he has been rarely seen in public, although he has continued to issue rulings.
In recent years, his brother, Abu Dhabi Crown Prince Mohammed bin Zayed, has been regarded as the de facto leader of the UAE.