St. George's Castle (Greek: Κάστρο Αγίου Γεωργίου, romanized: Kastro Agiou Georgiou; Turkish: Yeni kale, or Hizir kalesi) is an Ottoman fortification located in the city of Preveza, northwestern Greece.

It was built in 1807, during the rule of Ali Pasha of Ioannina over the region (1806-1820), and it was constructed on plans drawn by the French engineer Frédéric François Guillaume de Vaudoncourt (1772-1845).

For the construction, Ali Pasha hired two French military engineers; Captain Ponceton, and colonel Frédéric François Guillaume de Vaudoncourt [fr], to assist in the design and execution of the plan.

He, also, brought in several hundreds of Greek workers and stonemasons from many areas of his territory, who worked by compulsory labour and without pay for the project, which was concluded in less than a year's time.

Although the majority of the original early nineteenth-century structure survives, some aspects of the fort’s defensive features have been modified to accommodate the fortification’s use by the Greek military into the twentieth century.