Anastasius (Greek: Ἀρτέμιος Ἀναστάσιος Β΄), known in English as Anastasios II or Anastasius II, was the Byzantine Emperor from 713 to 715.
Anastasios was originally named Artemius (Ἀρτέμιος) and had served as a bureaucrat and Imperial secretary (asekretis) for his predecessors. After the Opsician army in Thrace had overthrown Emperor Philippikos Bardanes (Philippicus), they acclaimed Artemius as Emperor. He chose Anastasius as his regnal name. Soon after his accession, Anastasius II imposed discipline on the army and executed those officers who had been directly involved in the conspiracy against Philippikos.
The advancing Umayyad Caliphate surrounded the Empire by land and sea (they penetrated as far as Galatia in 714), and Anastasios attempted to restore peace by diplomatic means. His emissaries having failed in Damascus, he undertook the restoration of Constantinople's walls and the rebuilding of the Roman fleet. However, the death of the Caliph al-Walid I in 715 gave Anastasius an opportunity to turn the tables on his rival. He dispatched an army under Leo the Isaurian, afterwards emperor, to invade Syria, and he had his fleet concentrate on Rhodes with orders not only to resist the approach of the enemy but to destroy their naval stores.
These troops of the Opsician theme, resenting the Emperor's strict measures, mutinied, slew the admiral John, and proclaimed as emperor Theodosius III (Theodosios), a tax-collector of low extraction. After a six-month siege, Constantinople was taken by Theodosius; Anastasios, who had fled to Nicaea, was eventually compelled to submit to the new emperor in 716 and retired to a monastery in Thessalonica.