View source for 43 BC

=== By place ===

==== Roman Republic ====
* [[Roman consul|Consuls]]: [[Gaius Vibius Pansa Caetronianus]] and [[Aulus Hirtius]]. The [[Roman Senate]] confirms [[Augustus|Octavian]] as [[propraetor]] with joint responsibility for the campaign against Antony. Hirtius and Octavian mobilize [[troops]] for the march to [[Modena|Mutina]], while Pansa continues the [[Conscription|levy]]. Embassy dispatched to treat with Antony.
* [[January 7]] – [[Augustus|Octavian]] is given ''[[imperium]]'', marking the start of his public career.<ref name=":0">{{Cite book |last=Fishwick |first=Duncan |url=https://books.google.com/books?id=7Ox5DwAAQBAJ&pg=PA250 |title=The Imperial Cult in the Latin West III, Part 3 |date=2004 |publisher=Brill |isbn=9789047412762 |page=250}}</ref>
* [[Marcus Junius Brutus]] proceeds to secure his position in [[Thrace]] and [[Macedonia (Roman province)|Macedonia]]. [[Gaius Cassius Longinus]] campaigns in [[Syria]] and defeats the army of [[Publius Cornelius Dolabella (consul 44 BC)|Publius Cornelius Dolabella]] at [[Latakia|Laodicea]].
* March – Vibius Pansa set out to link up with Hirtius and Octavian, bringing four [[Roman legion|legions]] of [[Army recruit|recruits]], having left one, the ''legio urbana'', to defend [[Rome]].
* [[April 14]] – [[Battle of Forum Gallorum]]: [[Mark Antony]], besieging [[Julius Caesar|Caesar]]'s assassin [[Decimus Junius Brutus Albinus|Decimus Brutus Albinus]] in [[Mutina]], defeats the forces of the consul [[Gaius Vibius Pansa Caetronianus|Pansa]], but is then immediately defeated by the army of the other consul, [[Hirtius]]. Both consuls are killed (Hirtius does not die until after the [[Battle of Mutina]]).
* [[April 16]] – Octavian is first proclaimed ''[[imperator]]'' by his troops.<ref name=":0" />
* [[April 21]]
** [[Cicero]]'s 14th and last ''[[Philippicae|Philippic]]''.
** Antony is again defeated in the [[Battle of Mutina]] by a coalition of [[Augustus|Octavian]], [[Decimus Junius Brutus Albinus|Decimus Brutus]], and the two consuls of the year. 
* Antony marches to [[Parma]] (which is sacked) and [[Piacenza|Placentia]]. He then crosses the [[Ligurian Alps]] to [[Vada Sabatia]], {{convert|50|km|0|abbr=on}} south-west of [[Genoa]], and joins with [[Marcus Aemilius Lepidus (triumvir)|Aemilius Lepidus]], soon after Decimus Brutus is killed by [[brigands]]. The Senate declares Antony a [[Hostis humani generis|hostis]], an enemy of the state. [[Sextus Pompey]] becomes supreme commander of the [[Roman navy]] and Gaius Cassius [[proconsul]] of [[Syria (Roman province)|Syria]].
* Summer &ndash; Gaius Cassius captures [[Rhodes]] after they refuse to pay [[tribute]]. Their fleet is defeated by [[Galley#Roman Imperial era|Roman galleys]] in the [[Aegean Sea]]. He lands a military force on the island and plunders the city. Cassius puts to death 50 of the leading citizens and seizes all the gold he can lay hands on.<ref>Warfare in the Classical World, John Warry (1980), p. 177. {{ISBN|0-8061-2794-5}}</ref> 
* July–August – Antony is again at the head of a large army; Octavian enters [[Rome]] in force without opposition. It is clear that Cicero's plan to divide them against each other has failed.
* [[August 19]] – [[Augustus|Octavian]] takes office as [[consul]]. He's prevailed to pass the ''lex Pedia'', a law establishing the murder of Caesar as a capital crime.
* [[November 26]] – Octavian meets Antony and [[Marcus Aemilius Lepidus (triumvir)|Lepidus]] in [[Bologna|Bononia]] and the three enter into an official five-year autocratic pact, the [[Second Triumvirate]] (see ''[[lex Titia]]''). To cement their reconciliation Octavian agrees to marry [[Claudia (wife of Octavian)|Claudia]], a daughter of Antony's wife [[Fulvia]] by her former husband [[Publius Clodius Pulcher]].
* November – The triumvirs introduce [[proscriptions of the Second Triumvirate|proscriptions]] in which allegedly 130 senators and 2,000 ''[[Equestrian order|equites]]'' are branded as [[outlaw]]s and deprived of their property.
* [[December 7]] – The orator [[Cicero]] is killed in [[Formiae]] in a [[Litter (vehicle)|litter]] going to the seaside, by a party led by Herennius (a [[centurion]]) and Popilius (a military [[tribune]]). His head and hands are displayed on the [[Rostra]] in the [[Forum Romanum]].<ref>Haskell, H. J. (1964). ''This was Cicero''. p. 293.</ref>

==== Gaul ====
* [[Lugdunum]] (modern-day [[Lyon]]) is founded.
* First reference to [[Cularo]] ([[Grenoble]]).

==== Asia ====
* According to legend, [[Nagasena]] creates the [[Emerald Buddha]] figurine in [[Patna]], India.

==== North America ====
* [[Mount Okmok]] volcano in the Aleutian Islands erupts with a [[volcanic explosivity index]] of 6, with climatic effects extending as far as Egypt.<ref>{{cite journal |last1=McConnell |first1=Joseph R. |display-authors=1 |last2=Sigl |first2=Michael |last3=Plunkett |first3=Gill |last4=Burke |first4=Andrea |last5=Kim |first5=Woon Mi |last6=Raible |first6=Christoph C. |last7=Wilson |first7=Andrew I. |last8=Manning |first8=Joseph G. |last9=Ludlow |first9=Francis |last10=Chellman |first10=Nathan J. |last11=Innes |first11=Helen M. |last12=Yang |first12=Zhen |last13=Larsen |first13=Jessica F. |last14=Schaefer |first14=Janet R. |last15=Kipfstuhl |first15=Sepp |last16=Mojtabavi |first16=Seyedhamidreza |last17=Wilhelms |first17=Frank |last18=Opel |first18=Thomas |last19=Meyer |first19=Hanno |last20=Steffensen |first20=Jørgen Peder |title=Extreme climate after massive eruption of Alaska's Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom |journal=Proceedings of the National Academy of Sciences |date=7 July 2020 |volume=117 |issue=27 |pages=15443–15449 |doi=10.1073/pnas.2002722117 |doi-access=free |pmid=32571905 |language=en|pmc=7354934 |bibcode=2020PNAS..11715443M }}</ref></onlyinclude>