The last years of Galerius see him relinquishing his aspirations towards being the supreme emperor of the empire, though he manages to retain the position of first among equals.

Having thus moderated his ambition, he retires to the city Felix Romuliana (near present day Gamzigrad, Serbia) built by him to honor his mother Romula, and plans to devote the few remaining years of his life to enjoyment and ordering such significant public works as discharging into the Danube the superfluous waters of Lake Pelso (now lake Balaton), and the cutting down of the immense forests that encompass it.

Galerius, a ruthless ruler, has imposed the poll tax on the urban population, maintained the persecution of the Christians that Diocletian had initiated, and managed to hold together an empire riven by civil war in the West.

In the winter of 310-311, however, he becomes incapacitated with a painful disease.

On April 30, 311—perhaps fearing that his illness is the vengeance of the Christian God—he issues an edict grudgingly granting toleration.

Shortly afterward, he dies.