Assuming the new executive presidency he has long fought to establish, Erdogan took the oath of office in parliament before addressing dozens of international leaders gathered at the presidential palace in Ankara.
Erdogan, 64, says the new, powerful executive presidency is vital to drive economic growth, ensure security after a failed 2016 military coup and safeguard from conflict across the southern border in Syria and Iraq.
The introduction of the new presidential system marks the biggest overhaul of governance since the Turkish republic was established on the ruins of the Ottoman Empire nearly a century ago.
The post of prime minister has been scrapped and the president will now be able to select his own cabinet, regulate ministries and remove civil servants, all without parliamentary approval.
Erdogan’s supporters see the changes as a just reward for a leader who has put Islamic values at the core of public life, championed the pious working classes and overseen years of strong economic growth.
Opponents say the move marks a lurch to authoritarianism, accusing Erdogan of eroding the secular institutions set up by modern Turkey’s founder, Mustafa Kemal Ataturk, and driving it further from Western values of democracy and free speech.
Erdogan will name a streamlined cabinet of 16 ministers on Monday evening after the ceremony at the presidential palace, which state news agency Anadolu said was attended by Venezuelan President Nicolas Maduro, Russian Prime Minister Dmitry Medvedev and Sudan’s President Omar Hassan al-Bashir, who is wanted for war crimes by the International Criminal Court.
No major Western leader featured on a list of 50 presidents, prime ministers and other high-ranking guests.