Voting is under way across Turkey for the country's first ever presidential election put to a popular vote.
Three candidates are vying for the position, including current Prime Minister Recep Tayyip Erdogan.
If none of the candidates gets above 50% of the vote, a second round will be held on 24 August.
Mr Erdogan, 60, says that if he wins he wants to turn the largely ceremonial post of president into the country's executive powerhouse.
He has been prime minister since 2003 and is barred from standing for that office again.
Polls opened at 08:00 local time (05:00 GMT) and close at 17:00.
'Show our colours'
The BBC's Mark Lowen in Ankara says Mr Erdogan is a divisive figure adored by his supporters for transforming the economy but hated by critics for an abrasive style and Islamist leanings.
Turkey - wedged between the turmoil of Iraq, Syria and Ukraine - is an important ally for the West, our correspondent adds, and whoever becomes head of state will hold a key geopolitical position.
Read more, plus video report: http://www.bbc.co.uk/news/world-europe-28729234