AD 42 (XLII) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. At the time it was known as the Year of the Consulship of Caesar and Largus (or, less frequently, year 795 Ab urbe condita). The denomination AD 42 for this year has been used since the Early Middle Ages, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

This article does not cite any sources. (February 2016)

• Herennius Philo, Greek grammarian and writer (d. 141)
• Sixtus I, pope of the Catholic Church (d. 124)

• Arria, Roman noblewoman (committed suicide)
• Aulus Caecina Paetus, Roman politician (committed suicide)
• Gaius Appius Junius Silanus, Roman consul (executed)
• Lucius Annius Vinicianus, Roman politician (committed suicide)
• Lucius Arruntius Camillus Scribonianus, Roman politician (committed suicide)