The 40s BC were the period 49 BC – 40 BC.
Significant people
- Julius Caesar, Roman dictator (lived 100–44 BC, term 46–44 BC)
- Marcus Junius Brutus, Roman politician (85–42 BC)
- Mark Antony, Roman politician and general (83–30 BC)
- Pharaoh Cleopatra VII of Egypt (lived 70/69–30 BC, reigned 51–30 BC)—enters her twenties, has son Caesarion with Julius Caesar, before meeting Mark Antony
- Gaius Iulius Caesar Octavianus, Roman politician and general (62 BC–AD 14)
- Pharaoh Ptolemy XV Caesarion (lived 47–30 BC, reigned 44–30 BC)
- Gaius Cassius Longinus, Roman politician (died 42 BC)