Legio XV Primigenia Roman vexillum

Legio XV Primigenia was a relatively late foundation legion, created by Emperor Caligula in 39 AD along with its "twin" XXII Primigenia, and dedicated to the goddess Fortuna Primigenia, particularly revered at court. Initially intended for the major Germanic offensive planned by the princeps, it crossed the Alps in the autumn of 39 to be stationed along the Rhine, in the Germanic area, where it remained for its entire short existence.

Its main castrum was Castra Vetera, near modern-day Xanten, a strategic hub for controlling Germanic tribes and waterways.

During the Year of the Four Emperors, the XV Primigenia sided with Vitellius, participating in his campaigns against Galba and then Otho, confirming the strong political weight of the legions on the Rhenish frontier. Upon returning to Castra Vetera, it was involved in the Batavian Revolt of 69–70, when the Batavians, exploiting civil chaos, besieged the camp. Despite the dispatch of reinforcements, the XV Primigenia, along with the V Alaudae, was forced to surrender in March 70 and subsequently annihilated, being formally disbanded under Vespasian.