Year 242 (CCXLII) was a common year starting on Saturday of the Julian calendar. At the time, it was known as the Year of the Consulship of Gratus and Lepidus (or, less frequently, year 995 Ab urbe condita). The denomination 242 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.

• Emperor Gordian III begins a campaign against King Shapur I, and leads victories at Antioch, Carrhae, Nisibis, and Resaina.^[1]
• Gordian III evacuates the Cimmerian cities in the Bosphorus (Crimea), as the territory is now controlled by the Goths.

• Shapur I makes a pre-emptive attack on Antioch to drive out the Romans. Gordian's father-in-law, Timesitheus, leads a Roman army to defeat the Sassanids at Carrhae and Nisibis.
• King Ardashir I, founder of the Sassanid Empire, dies after a 30-year reign. He is succeeded by his son and co-ruler Shapur I.

• Patriarch Titus succeeds Eugenius I as Patriarch of Constantinople (until 272).

• Saloninus, Roman emperor (d. 260)

• Ammonius Saccas, Egyptian philosopher (b. 175)
• Ardashir I, king of the Sassanid Empire (b. 180)
• Cao Hui, Chinese prince of the Cao Wei state
• Man Chong (or Boning), Chinese politician