For the first-century bishop, see Anianus of Alexandria.

Annianus of Alexandria was a monk who flourished in Alexandria during the bishopric of Theophilus of Alexandria around the beginning of the fifth century. He criticized the world history of his contemporary monk Panodorus of Alexandria for relying too much on secular sources rather than biblical sources for his dates. Thus he developed his own timeline which placed Creation on 25 March 5492 BC. This created the Alexandrian Era whose first day was the first day of the proleptic Alexandrian civil year in progress, 29 August 5493 BC. This year was eleven Paschal cycles of 532 years each before the Alexandrian year beginning 29 August 360, which itself was four 19-year cycles after the epoch of the Diocletian Era on 29 August 284. The former is known as the Era of Grace in the Coptic Church, whereas the latter is known as the Era of Martyrs. He was the first computist to recognize the 532-year cycle of Easters in the Julian calendar. This cycle is often attributed to Victorius of Aquitaine in 457, the first to recognize such a cycle in the West (Aquitaine is a region in southwest France). None of his writings have survived — he is known only from the discussion of his works by George Syncellus during the ninth century.