United Arab Emirates President Sheikh Khalifa Bin Zayed Al Nahyan has died aged 73.
Sheikh Khalifa, who was also ruler of Abu Dhabi emirate, was rumoured to be worth $15billion, which is around £12.3billion.
Sheikh Khalifa's death marks the beginning of 40 days of mourning in the UAE.
The country's Ministry of Presidential Affairs said: “The Ministry of Presidential Affairs mourns the death of the nation’s President His Highness Sheikh Khalifa bin Zayed Al Nahyan.”
Sheikh Khalifa Bin Zayed Al Nahyan
Stephanie McGehee
Under the constitution, vice-president and premier Sheikh Mohammed bin Rashid al-Maktoum, ruler of Dubai, will act as President until the federal council, which groups the rulers of the seven emirates, meets within 30 days to elect a new president.
Sheikh Khalifa, who was born in 1948, came to power in 2004 in the richest emirate Abu Dhabi and became the head of state.
He was the second President of the UAE and the 16th Ruler of the Emirate of Abu Dhabi.
He is expected to be succeeded as ruler of Abu Dhabi by his half-brother Crown Prince Sheikh Mohammed bin Zayed al-Nahyan.
Mohammed bin Zayed has been the de facto ruler of the US-allied UAE, particularly after Khalifa suffered a stroke in 2014, following which he has rarely been seen in public.