Barnabas (; Syriac: ܒܪܢܒܐ; Ancient Greek: Βαρνάβας), born Joseph (Ἰωσήφ) or Joses (Ἰωσής), was according to tradition an early Christian, one of the prominent Christian disciples in Jerusalem. According to Acts 4:36, Barnabas was a Cypriot Jew. Named an apostle in Acts 14:14, he and Paul the Apostle undertook missionary journeys together and defended Gentile converts against the Judaizers. They traveled together making more converts (c. 46–48), and participated in the Council of Jerusalem (c. 49). Barnabas and Paul successfully evangelized among the "God-fearing" Gentiles who attended synagogues in various Hellenized cities of Anatolia.

Barnabas' story appears in the Acts of the Apostles, and Paul mentions him in some of his epistles. Tertullian named him as the author of the Epistle to the Hebrews, but this and other attributions are conjecture. The Epistle of Barnabas was ascribed to him by Clement of Alexandria and others in the early church and the epistle is included under his name in Codex Sinaiticus, the earliest extant manuscript of the complete New Testament. A few modern scholars concur with this traditional attribution but it is presently a minority view.

Although the date, place, and circumstances of his death are historically unverifiable, Christian tradition holds that Barnabas was martyred at Salamis, Cyprus. He is traditionally identified as the founder of the Cypriot Orthodox Church. The feast day of Barnabas is celebrated on June 11.

Barnabas is usually identified as the cousin of Mark the Evangelist on the basis of the term "anepsios" used in Colossians 4, which carries the connotation of "cousin." Orthodox tradition holds that Aristobulus of Britannia, one of the Seventy Disciples, was the brother of Barnabas.