Ploiesti, formerly spelled Ploesti, is a city and county seat in Prahova County, Romania.

Part of the historical region of Muntenia, it is located 56 km (35 mi) north of Bucharest. The area of the city is around 60 km². It borders the Blejoi commune in the North, Barcanesti and Brazi communes in the South, Târgsoru Vechi in the West and Bucov and Berceni communes in the East. Ploiesti has direct access to the Prahova Valley, one of the most important alpine tourism areas in Romania.

Ploiesti is an important transport hub, linking Bucharest with Transylvania and Moldavia. According to the 2011 Romanian census, there were 201,226 people living within the city of Ploiesti, making it the 9th most populous in the country.