Sheikh Mohamed bin Zayed, Ruler of Abu Dhabi, has been elected the country's president.
The official announcement followed a meeting in Abu Dhabi of the rulers of the Emirates.
He becomes the third president in the UAE's history, following the death of Sheikh Khalifa on Friday.
State news agency Wam reported the decision by the Federal Supreme Council, which comprises the rulers of which comprises the rulers of the seven emirates.
The President, Sheikh Mohamed “expressed his appreciation for the dear trust that his brothers, their highnesses, members of the Federal Supreme Council, have entrusted him with, praying that Almighty God helps him succeed, helps him in taking on this great responsibility and meeting it in serving the UAE and its loyal people”, in comments published by Wam.
Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, offered his congratulations.
“Today, the Federal Supreme Council elected my brother, His Highness Sheikh Mohamed bin Zayed Al Nahyan, as President of the State,” he wrote on Twitter.
“We congratulate him and we pledge allegiance to him, and our people pledge allegiance to him.”
The council held a meeting at Mushrif Palace, Abu Dhabi, chaired by Sheikh Mohammed.
Present were Sheikh Mohamed bin Zayed, Sheikh Dr Sultan bin Muhammad Al Qasimi, Ruler of Sharjah, Sheikh Humaid bin Rashid Al Nuaimi, Ruler of Ajman, Sheikh Hamad bin Mohammed Al Sharqi, Ruler of Fujairah, Sheikh Saud bin Rashid Al Mualla, Ruler of Umm Al Quwain and Sheikh Saud bin Saqr Al Qasimi, Ruler of Ras Al Khaimah.
Sheikh Dr Sultan, Ruler of Sharjah, said: “As he has witnessed the UAE's renaissance from a young age, accompanied by the late Sheikh Zayed bin Sultan Al Nahyan, Sheikh Khalifa bin Zayed Al Nahyan, and the Founding Leaders, President His Highness Sheikh Mohamed bin Zayed Al Nahyan has significantly contributed to UAE's development and achievements due to his wise vision, constant support and direct guidance.
“We congratulate President His Highness Sheikh Mohamed bin Zayed Al Nahyan, and ask Allah Almighty to grant him success and prosperity.
“We affirm our permanent solidarity in serving the nation and preserving its union under his wise leadership.”
A statement by the Ministry of Presidential Affairs said that, according to Article 51 of the Constitution, Sheikh Mohamed bin Zayed was elected unanimously.
On Saturday, Sheikh Mohamed is receiving condolences over the death of his brother Sheikh Khalifa from the rulers and senior Emirati officials.
Foreign diplomats and leaders are expected to visit to pay their respects and meet the new president in the coming days.
Dr Anwar Gargash, diplomatic adviser to the President, said: “The smooth transition of power in the UAE reflects the strength of institutional work and the advanced standards of governance and stability.
“We thank God for the blessing of the UAE and pledge allegiance to Sheikh Mohamed bin Zayed. May God protect him as President and leader.”