The Roman emperor who completed the conquest of Dacia in 106 AD was Trajan.
Trajan’s second war against Dacia ended in 106 AD with the defeat of the Dacian king Decebalus and the incorporation of much of Dacia into the Roman Empire. The campaign followed an earlier war in 101–102, after which Decebalus had accepted client-king status but retained substantial power. Renewed conflict began when that settlement broke down.
Dacia, north of the Danube, had long concerned Rome because of its military strength, resources, and position near the empire’s Balkan provinces. Trajan’s victory expanded Roman territory across the Danube and brought valuable gold and other resources under imperial control. Rome organized the conquered territory as the province of Dacia, although some Dacian regions remained outside direct Roman rule.
Trajan commemorated the campaigns in Rome with Trajan’s Column, completed around 113 AD. Its spiral reliefs depict scenes from the Dacian Wars and provide one of the best-known visual records of Roman military campaigning. Hadrian, who succeeded Trajan, later abandoned parts of Dacia, but he did not conquer it.