Year 40 BC was either a common year starting on Thursday, Friday or Saturday or a leap year starting on Thursday or Friday of the Julian calendar. At the time, it was known as the Year of the Consulship of Calvinus and Pollio.
|Millennium:||1st millennium BC|
|Centuries:||2nd century BC – 1st century BC – 1st century|
|Decades:||70s BC 60s BC 50s BC – 40s BC – 30s BC 20s BC 10s BC|
|Years:||43 BC 42 BC 41 BC – 40 BC – 39 BC 38 BC 37 BC|
|Gregorian calendar||40 BC|
|Ab urbe condita||714|
|Ancient Egypt era||XXXIII dynasty, 284|
|- Pharaoh||Cleopatra VII, 12|
|Ancient Greek era||185th Olympiad (victor)¹|
|Balinese saka calendar||N/A|
|Chinese calendar||庚辰年 (Metal Dragon)|
2657 or 2597
— to —
辛巳年 (Metal Snake)
2658 or 2598
|Coptic calendar||−323 – −322|
|Ethiopian calendar||−47 – −46|
|- Vikram Samvat||17–18|
|- Shaka Samvat||N/A|
|- Kali Yuga||3061–3062|
|Iranian calendar||661 BP – 660 BP|
|Islamic calendar||681 BH – 680 BH|
|Julian calendar||40 BC|
|Minguo calendar||1951 before ROC|
|Seleucid era||272/273 AG|
|Thai solar calendar||503–504|
87 or −294 or −1066
— to —
88 or −293 or −1065
- Lucius Antonius surrenders to Octavian in the Siege of Perusia
- Octavian divorces Clodia Pulchra and marries Scribonia
- Sextus Pompey captures Sardinia
- Treaty of Brundisium: The Roman Republic is divided. Gaius Octavian takes control of the Western provinces. Mark Antony is given the Eastern provinces. Marcus Aemilius Lepidus controls Hispania and Africa.
- Quintus Labienus occupies Cilicia and marches with an army into Anatolia.
- Parthians conquer Jerusalem. Hyrcanus II is removed from power.
- Herod the Great flees Jerusalem to Rome. There he is titled king of Judea by Mark Antony.
- Cleopatra Selene (d. AD 6) and Alexander Helios (d. between 29 and 25 BC), the twins of Cleopatra VII of Egypt and Mark Antony
- Gaius Claudius Marcellus Minor dies, leaving Octavia Minor widowed. She will later marry Mark Antony by decree of the Roman Senate (b. 88 BC)
- Fulvia, wife of Publius Clodius Pulcher