Turkey's governing party is likely to lose control of Istanbul following a repeat of mayoral elections, as initial results show. counted the votes.
He won a surprise victory in March, which was canceled after the ruling AK party objected to irregularities.
The vote is considered a key check for President Recep Tayyip Erdogan.
- Ambitious mayor takes over as Turkish president
Mr Imamoglu received 53.6% of the votes cast, according to state news agency Anadolu.
Who are the candidates?
Mr. Imamoglu, 49, is a member of the secular Republican People's Party and is the mayor of Istanbul Beylikduzu.
His name was barely known, however, before he ran for mayor in the March Elections.
His opponent, Binali Yildirim, was founding member of AKP of Mr. Erdogan and Prime Minister from 201
He was elected Speaker of the new Parliament in February and was previously Minister of Transport and Communications.