Constantius Chlorus (250-306) was born into a noble framily from Dardania descended from emperors Claudius II and Quintillus; though this may have been a genealogical fabrication by Constantius' son Constantine I; with his real family instead being of humble origins.

Constantius joined the Roman army and served under various emperors; eventually being elevated to junior co-emperor alongside Galerius in 293; forming the Tetrarchy. His marriage to Emperor Maximian's daughter made him his son-in-law; and together they defeated the rebel emperor Allectus in Britain and campaigned heavily along the Rhine frontier against various Germanic tribes.

In 305; Diocletian and Maximian abdicated; elevating Constantius and Galerius to joint emperors. Constantius was fighting the Picts in Britain beyond the Antonine Wall when the declaration came; but he died suddenly a year later in Eboracum (York). His death led to the collapse of the Tetrarchy. His son would become Constantine the Great; and therefore Constantius was considered the founder of the Constantinian Dynasty.