Year 123 (CXXIII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Paetinus and Apronius (or, less frequently, year 876 Ab urbe condita). The denomination 123 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

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• Annia Cornificia Faustina, sister of Marcus Aurelius (d. 158)