Sheikh Hamdan bin Rashid Al Maktoum, who had also been UAE’s finance minister since 1971, had been unwell in recent months and had undergone surgery in October.
Sheikh Hamdan bin Rashid Al Maktoum, Dubai's deputy ruler and the United Arab Emirates' long-serving finance minister, has died, Dubai's ruler said.
Sheikh Hamdan, 75, was the brother of the ruler of Dubai, Sheikh Mohammed bin Rashid al Maktoum. He had been unwell for some months and had surgery abroad in October.
Dubai's ruler bid farewell to "my brother, my support, my lifelong friend".
The UAE's de facto ruler, Abu Dhabi Crown Prince Mohammed bin Zayed al Nayhan, tweeted: "Today we lost one of the UAE's faithful men after a life rich with giving and true patriotic work."
Funeral prayers will be restricted to family members due to the Covid-19 pandemic, the Dubai Media Office said.
Dubai announced 10 days of mourning with flags to be flown at half-mast and a closure of government institutions in the emirate for three days as of Thursday.
In 2008, Dubai's ruler established the line of succession in the emirate by naming his son Hamdan, 38, as crown prince. His other son Maktoum is also a deputy ruler of Dubai.
The emirate, part of the UAE federation, is the Middle East's business, trade and tourism hub.
& members of the royal family on the passing of Sheikh Hamdan bin Rashid Al Maktoum, Deputy Ruler of Dubai and Minister of Finance, May his soul rest in peace.— Dubai Islamic Bank (@DIBtoday) March 24, 2021
Sheikh Hamdan enjoyed huge success on the racecourse, winning both the Epsom Derby and the Melbourne Cup twice.
His blue-and-white colours were most recently carried to glory by champion sprinter Battaash last year.
Aside from spending liberally at the horse sales each year he was also a successful breeder and generous sponsor of races.
Sheikh Hamdan also owned three stud farms, in England, Ireland and in the hotbed of thoroughbred breeding in the United States, Kentucky.
His two Derby successes came with Nashwan (1989) and Erhaab (1994) while his Melbourne Cup successes were with At Talaq (1986) and Jeune (1994).
Following this morning’s sad news, we wish to send our condolences to all @ShadwellStud. Many horses from the valley have enjoyed success in His Highness Sheikh Hamdan al Maktoum’s famous blue and white silks and his contribution to our industry has been immense. pic.twitter.com/dLtDWEsDtz— Lambourn Gallops (@LambournGallops) March 24, 2021
Richard Hills rode many winners for Sheikh Hamdan before assuming the role of assistant racing manager at his Shadwell operation.
"It's very sad news," he said in comments carried in the Racing Post. "It's like losing a boss and a father as I've known Sheikh Hamdan my whole life.
"He was such a good man and we were very close.
"I know he was very frustrated about not being able to come to Royal Ascot last year when we had six winners as he loved Ascot. He'll be sorely missed."
Sheikh Hamdan was patron of the Arabian Racing Organisation and the motivating force behind the establishment of the Dubai International Arabian Races, Europe's premier Arabian racing programme which has its finals day at Newbury racecourse each year.