Justin II ( died 4 October 578) was Eastern Roman emperor from 565 until 578. He was the nephew of Justinian I and the husband of Sophia, the niece of Justinian's wife Theodora.
Justin II inherited a greatly enlarged but overextended empire, with far fewer resources at his disposal compared to Justinian I. He ended the payment of tributes and adopted a hardline stance against the empire's neighbours, which resulted in both the rekindling of war with the Sassanid Empire in 572, and the initiation of the Byzantine-Lombard wars in 568, which by its end in 750 cost the Romans much of their territory in Italy. His war against the Persians was generally unsuccessful, and his later reign was marked by severe mental illness.