Milecastle 33 (Shield on the Wall) was a milecastle of the Roman Hadrian's Wall, one of a series of small fortlets built at intervals of approximately one Roman mile along the length of the UNESCO World Heritage Site in northern England.

Exposed parts survive to a maximum height of 1.2 metres (3 ft 11 in) (north wall).

[6] In plan, the turret has an entrance to the east end of the south wall, with a platform in the south-west corner, and a hearth at the centre.

[3] Material used for the blocking of the rear recess mentioned below included an inscribed stone naming the Legio VI Victrix.

[3] There is evidence that the following changes occurred during occupation: Occupation evidence includes jars and cooking pots (Hadrianic), butchered remains of young animals (cows, sheep and pigs), and the dumping of ashes from the hearth outside the east wall.