Ploiesti is the capital city of Prahova County, Romania. The city is located 56 km (35 miles) north of Bucharest and has a population of 232,452 (according to the 2002 census), making it the ninth-largest city in Romania.

The city was founded in 1596, during the reign of Mihai Viteazul (Michael the Brave). In the mid-19th century, the Ploiesti region became one of the most important oil extraction and refinery sites in the world. The city is also remembered as the site of the Republic of Ploiesti, a short-lived 1870 revolt against the Romanian Monarchy. Ploiesti oil storage tanks on fire after being bombarded by the United States Army Air Forces in Operation Tidal Wave, August 1943. The city was badly damaged by an earthquake in 1940, but managed to become the main source of oil for Nazi Germany during World War II, when Romania was allied to Germany. Following the war, the new Communist regime nationalized the oil industry, which had largely been privately owned, and made massive investments in the oil and petroleum industry in a bid to modernize and repair the war damage.

After the Romanian Revolution of 1989, Ploiesti has experienced rapid economic growth due to major investments from foreign companies, including Lukoil, Unilever, Coca-Cola, Interbrew and British American Tobacco. Ploiesti is also a developed textile manufacturing center. Although oil production in the region is constantly declining, there is still a flourishing processing industry that includes four oil refineries linked by pipelines to Bucharest, the Black Sea port of Constanta and the Danube port of Giurgiu.

Ploiesti is an important railway center linking Bucharest with Transylvania and Moldavia. The public transport system of Ploiesti is run by Regia Autonoma de Transport Ploiesti (RATP), and includes an extensive network of buses, trolleybuses and trams. Ploiesti's distinctive yellow bus fleet is one of the most modern in Southeastern Europe.

Ploiesti is home to the Oil & Gas University, Ploiesti Philharmonic Orchestra —one of the top rated philharmonic orchestras in Romania, two formerly-First Division football (soccer) clubs (Astra and Petrolul) and also some very unique museums:
• Oil National Museum - Ploiesti, unique in the country and also quite rare in the world;
• " Nicolae Simarche" Clock Museum - Ploiesti, a unique museum in Romania, it offers the visitors the opportunity to follow the evolution of the time measuring devices from the first "clocks"-sun dials, burning clocks, clocks with water or sand to the "ancient" mechanical clocks and the modern ones;
• History and Archeology Museum Prahova: The museum is housed in an imposing building, historical and architectural monument, hosting coins collection and medals collection, the room dedicated to the writer I.A. Bassarabescu and the Lapidarium. Lately, it was enriched with the hall "Mihai Viteazul si Ploiestii", the „Sport in Prahova county along the centuries" hall and a hall with archeological vestiges from Targsor Reservation.