Târgșor is a former medieval market town in what is now the Prahova County, Romania. The town peaked around 1600, after which it declined to become the village of Târgșoru Vechi.
Built in a heavily forested area, Târgșor developed thanks to the local fair and its auspicious location at a crossroad of several trade routes. These roads included Drumul Brăilei, which linked Târgoviște to the Danube port of Brăila, as well as the roads which linked Târgșor to Brașov and Bucharest.
Târgșor gets its name from the diminutive of târg (market, fair) and can be related to the name of Târgoviște, which was the capital of Wallachia and a much bigger city. The settlement transformed into a town sometimes between 1368 and 1412, during the rule of Mircea I; the first document mentioning his name: a September 1412 document by Voivode of Transylvania Stibor of Stiboricz, who granted the people of Brașov the "privileges of yore and worthy liberties".
Soon after, the merchants of Târgșor were granted trade privileges by Wallachia. The town was ruled by a județ and 12 pârgari. Unlike other Wallachian cities at the time, in Târgșor there were no traces of German colonists, nor a Catholic church.
The prince of Wallachia had a residence in Târgșor, which was probably built in the 16th century. While only Neagoe Basarab (ruled 1512-1521) refers to Târgșor as a seat, there are hints that the residence was earlier, as the church in the town, built by Vladislav II was called the Princely Church (Biserica Domnească). The residence decayed by 1600 and nowadays, only its ruined church survives. Recent archaeological research showed that the ruins thought to be the palace belonged to another church, Church of St. Nicholas, built by Vlad the Monk, while the palace's location has yet to be established.