Candidate of the governing AK Party (also known as AKP, or Justice and Development Party) and former prime minister Binali Yildirim, was narrowly defeated in the initial vote in March and a new mayor, opposition candidate Ekrem Imamoglu, took office.
However, Turkey's High Election Board cancelled the election results and set the rerun for 23 June after AKP said the balloting was marred by irregularities and fraud.
President Recep Tayyip Erdogan has also claimed that many votes had been stolen from AKP during the voting in Istanbul.
Recent surveys showed Yildirim had a chance to win the race.