Presian (Bulgarian: Пресиян, Персиян) was the ruler of Bulgaria in 836–852. The Byzantine sources indicate that Presian I was the son of Zvinica (Zbēnitzēs), who was a son of Omurtag.
Presian may have been young and inexperienced at the time of his accession, and state affairs may have been dominated by the minister (kaukhanos) Isbul, as under Presian's uncle Malamir.
Soon after Presian's accession, the Slavs in the vicinity of Thessalonica rebelled against the Byzantine Empire in 837. Emperor Theophilos sought Bulgarian support in putting down the rebellion, but simultaneously arranged for his fleet to sail through the Danube delta and undertake a clandestine evacuation of some of the Byzantine captives settled in trans-Danubian Bulgaria by Krum and Omurtag.
In retaliation Isbul campaigned along the Aegean coasts of Thrace and Macedonia and captured the city of Philippi, where he set up a surviving memorial inscription set up in a local church.
Presian's reign apparently coincides with the extension of Bulgarian control over the Slavic tribes in and around Macedonia. However, Presian's campaigns against the Serbs in about 839–842 failed. By the end of Presian's reign Serbia and Bulgaria lived in an uneasy peace.