Recep Tayyip Erdogan is taking the oath of office as Turkey's first popularly elected president, a position that will keep him in the nation's driving seat for at least another five years.
Taking over Erdogan's post of prime minister is Foreign Minister Ahmet Davutoglu, a long standing ally who is expected to do little to challenge the Turkish number one.
Heads of state from a dozen nations in Eastern Europe, Africa, Central Asia and the Middle East will attend the ceremony, including Ukraine's President Petro Poroshenko, the Anatolia news agency reported.
But leaders of top Western states will be conspicuous by their absence in a possible sign of suspicion towards Erdogan, who has been accused of authoritarian tendencies. The United States is only sending its charge d'affaires in Ankara.
Armenian Foreign Minister Edward Nalbandian, whose country has no diplomatic ties with its giant neighbor, is expected to attend the ceremony.
Erdogan, who became prime minister in 2003, won presidential elections on August 10 against a weak opposition, which accuses him of Islamizing tendencies but remains in disarray.
A man clearly with his eye on history, Erdogan during his five-year presidential term will have ruled Turkey longer than its modern founder Mustafa Kemal Ataturk, who established the republic out of the ruins of the Ottoman Empire.
He can serve two mandates and so could stay in power until 2024, which would allow him to see in the 100th anniversary of modern Turkey in 2023 and portray himself as a historic figure rivaling Ataturk.
Davutoglu was confirmed as party leader at a vast meeting of the ruling Justice and Development Party (AKP) at which both men vowed there would be no change in policy, despite the changeover.
"Names have no importance. Names change today but our essence, our mission, our spirits, our goals and ideals remain in place," Erdogan told the meeting.
Erdogan, who has two sons and two daughters, described the party he helped found as his "fifth child," but said the "farewell time" had come.
Under Turkish law, the president should sever all ties with political parties -- but Erdogan said the party was not just about one person.
"The AKP will never be a one-man party. It is a party of principles," he said.
Erdogan, however, insisted that Davutoglu would be a figure of real stature and power as prime minister.
"I would like to stress this: Davutoglu is not a caretaker. Everyone should know that."
Davutoglu said that there would be no conflict with Erdogan and the two would build a new Turkey "hand-in-hand."
"We will build the new Turkey hand-in-hand, shoulder-to-shoulder. No one can sow the seeds of animosity between comrades."
Showing his combative side, Davutoglu slammed anti-government protests that erupted last year over the redevelopment of an Istanbul park as an attempt "to destroy the self-confidence that we have instilled in our people."
He vowed to build a strong Turkey that would flourish and would not collapse like the Ottoman Empire after World War I.
"We will not let Turkey face the big disaster that the Ottoman Empire has faced."
Davutoglu will form a new cabinet by Friday, with intense speculation over who will hold the top jobs.
Press reports have tipped the head of Turkey's intelligence service Hakan Fidan as a possible new foreign minister, while there is also huge attention on the future of economic pointman and market favorite Ali Babacan in the government.
Davutoglu, who became foreign minister in 2009, is a controversial figure blamed by some for pursuing an over-ambitious foreign policy that led to the rise of Islamic militants in Syria.