Athanasius I may refer to:
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Athanasius of Alexandria (c. 293 – 373), also called Pope Athanasius I of Alexandria, Christian theologian
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Athanasius I Gammolo (died 631), Syriac Patriarch of Antioch
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Athanasius I (bishop of Naples) (830–872)
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Athanasius I of Constantinople
Athanasius I (1230 – 28 October 1310) was the Ecumenical Patriarch of Constantinople for two terms, from 1289 to 1293 and 1303 to 1309. He was born in Adrianople and died in Constantinople. Chosen by the emperor Andronicus II Palaeologus
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(1230–1310), Ecumenical Patriarch of Constantinople
{{hndis, Athanasius 01