Šumber (Italian: Sumber, Sumberg, Casali Sumberesi) is a village and ruinous castle in the eastern part of Istria County, Croatia, in the municipality of Sveta Nedelja.

The site was first mentioned in documents in 872, and in 950 when Byzantine Emperor Constantine VII Porfirogenet confirmed the presence of Slavs in these villages.

Among the signatories of the peace treaty in 1274 between the Aquleia patriarch Raimondo della Torre and the Count of Gorizia Albert I, there was Teodorich de Sumberg.

As a vassal of Gorizia Count Albert III, Dietrich von Schonberg in 1341 attack and plundered the countryside of Venetian Motovun.

It's a small fortress with polygonal layout defended by two round half-towers in south-eastern and south-western part, next to which is on the west wall the main entrance to the fort.

On the inner side of the southern wall are the remains of a long and narrow one-story palace, and another small house is located in the northeast corner of the castle.