The Nijmegen Helmet is an Ancient Roman helmet, found in a gravel bed on the left bank of Waal river, near the Dutch city of Nijmegen in 1915. The helmet would have been worn by the elite Roman cavalry. The head portion of the helmet is made of iron, while the mask and diadem are of bronze or brass. The helmet has a neck-protecting projecting rim, overlaid with a thin bronze covering plated with silver. The diadem features two male and three female figures from the cult of Bacchus.

The mask was attached to a cavalry soldier’s helmet by a hinge and worn on parade—and perhaps into battle.