The Wars of Castro describe a series of events in the mid-seventeenth century revolving around the ancient city of Castro (located in present-day Lazio, Italy), which eventually results in the city's destruction on September 2, 1649.

The conflict is a result of a power struggle between the papacy — represented by members of two deeply entrenched Roman families, the Barberini Pope Urban VIII and then the Pamphili Pope Innocent X — and the Farnese dukes of Parma, who contro Castro and its surrounding territories.Papal politics of the mid-seventeenth century are complicated, with frequently shifting military and political alliances across the Catholic world.

While it is difficult to trace the precise origins of the feud between the duchy of Parma and the papacy, its origins can be looked for in political maneuverings occurring in the years or even decades preceding the start of military action.

The duke of Parma and his immediate family had narrowly escaped a planned mass assassination of the Farnese in 1611, for which ten high-born conspirators had been executed in the main square of Parma in May of the following year.Odoardo Farnese, Duke of Parma and Piacenza, who controls Castro, had quarreled with Pope Urban VIII's influential Barberini nephews during a visit to Rome in 1639.

These offended relatives of the Pope had convinced him to ban grain shipments originating in Castro from being distributed in Rome and the surrounding territory, thereby depriving Duke Odoardo of an important source of income.

As a result, Duke Odoardo is unable to pay debts due to Roman creditors, which he has accumulated in military adventures against the Spanish in Milan and in luxurious living.

These unpaid and unhappy creditors seek relief from the pope, who turns to military action in an attempt to force payment.