Year 427 (CDXXVII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Hierus and Ardabur (or, less frequently, year 1180 Ab urbe condita). The denomination 427 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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• Erbin of Dumnonia, Brythonic king (approximate date)
• Qi Gaodi, Chinese emperor of the Southern Qi Dynasty (d. 482)
• Wang Xianyuan, empress and wife of Song Xiaowudi (d. 464)
• Plato, Greek philosopher (or 428 BC)^[2]

• December 24 – Sisinnius I, archbishop of Constantinople
• Guisin, king of Baekje (Korea)^[1]
• Tao Qian, Chinese poet of the Eastern Jin Dynasty (b. 365)