The County of Guastalla was a sovereign state of northern Italy centred on Guastalla. The title of count was created in 1406 for Guido Torelli: the Torelli family held Guastalla until 1539, when it was bought by Ferrante Gonzaga. Another branch held the county of Montechiarugolo (created from a split in the county in 1456) until 1612. Ferrante's descendants ruled the country until 1746, being raised to the title of Duke in 1621. Duke Giuseppe Maria died heirless in 1746 and the country was briefly incorporated into Austrian Lombardy.
With the treaty of Aix-la-Chapelle (1748), Guastalla was ceded to the Duke of Parma.