|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:||52 BC 51 BC 50 BC – 49 BC – 48 BC 47 BC 46 BC|
|49 BC by topic|
|Gregorian calendar||49 BC
|Ab urbe condita||705|
|Ancient Egypt era||XXXIII dynasty, 275|
|- Pharaoh||Cleopatra VII, 3|
|Ancient Greek era||182nd Olympiad, year 4|
|Chinese calendar||辛未年 (Metal Goat)
2648 or 2588
— to —
壬申年 (Water Monkey)
2649 or 2589
|Coptic calendar||−332 – −331|
|Ethiopian calendar||−56 – −55|
|- Vikram Samvat||8–9|
|- Shaka Samvat||N/A|
|- Kali Yuga||3052–3053|
|Iranian calendar||670 BP – 669 BP|
|Islamic calendar||691 BH – 690 BH|
|Minguo calendar||1960 before ROC
|Seleucid era||263/264 AG|
|Thai solar calendar||494–495|
|Wikimedia Commons has media related to 49 BC.|
Year 49 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Lentulus and Marcellus (or, less frequently, year 705 Ab urbe condita). The denomination 49 BC 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.
- Consuls: Lucius Cornelius Lentulus Crus, Gaius Claudius Marcellus Maior.
- The Great Roman Civil War commences:
- January 1 – The Roman Senate receives a proposal from Julius Caesar that he and Pompey should lay down their commands simultaneously. The Senate responds that Caesar must immediately surrender his command.
- January 10 – Julius Caesar leads his army across the Rubicon, which separates his jurisdiction (Cisalpine Gaul) from that of the Senate (Italy), and thus initiates a civil war. In response, the Roman senate invokes the senatus consultum ultimum.
- February – Pompey's flight to Epirus (in Western Greece) with most of the Senate.
- March 9 – Caesar advances against Pompeian forces in Spain.
- April 19 – Siege of Massilia: Caesar commences a siege at Massilia against the Pompeian Lucius Domitius Ahenobarbus. He leaves the newly raised legions XVII, XVIII and XIX to conduct the siege. Decimus Brutus — victor over the Veneti (see 56 BC) — is in charge of the fleet to blockade the harbor.
- June – Caesar arrives in Spain; seizes the Pyrenees passes against the Pompeians L. Afranius and Marcus Petreius.
- June 7 – Cicero slips out of Italy and goes to Salonika.
- July 30 – Caesar surrounds Afranius and Petreius's army in Ilerda.
- August 2 – Pompeians in Ilerda surrender to Caesar and are granted pardon.
- August 24 – Caesar's general Gaius Scribonius Curio is defeated in North Africa by the Pompeians under Attius Varus and King Juba I of Numidia (whom he defeated earlier in the Battle of Utica), in the Battle of the Bagradas River, and commits suicide.
- September – Brutus defeats the combined Pompeian-Massilian naval forces in the naval Battle of Massilia, while the Caesarian fleet in the Adriatic is defeated near Curicta (Krk).
- September 6 – Massilia surrendered to Caesar, coming back from Spain.
- October – Caesar appointed Dictator in Rome.
- Gaius Scribonius Curio (suicide) (b. 90 BC)
- Xuan, emperor of the Chinese Han Dynasty (b. 91 BC)
- Zheng Ji, general during the Han Dynasty