Sheikha Hala bint Daij Al Khalifa, the wife of Bahrain’s crown prince, has died.
Her death was announced early on Sunday by the state-run Bahrain News Agency.
Sheikha Hala was married to Crown Prince Salman bin Hamad. They had four children.
Their son, Prince Isa bin Salman, is second in line to the throne after his father.
Sheikha Hala, although she kept a low profile, was known for her charity work, including the launch of an anti-child abuse programme in the kingdom in 2003.
Condolences flooded in from across the region led by UAE President Sheikh Khalifa, who sent a message to Bahraini King Hamad.
Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, and Sheikh Mohammed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the UAE Armed Forces, sent similar messages to King Hamad.
Bahrain's Foreign Minister Khalid bin Ahmad also offered his condolences on Sunday morning.
"May God have mercy on the good and kind [Shaikha Hala], for whom many will weep," he tweeted.