|Millennium:||1st millennium BC|
|105 BC by topic|
|Gregorian calendar||105 BC|
|Ab urbe condita||649|
|Ancient Egypt era||XXXIII dynasty, 219|
|- Pharaoh||Ptolemy X Alexander, 3|
|Ancient Greek era||168th Olympiad, year 4|
|Balinese saka calendar||N/A|
|Chinese calendar||乙亥年 (Wood Pig)|
2592 or 2532
— to —
丙子年 (Fire Rat)
2593 or 2533
|Coptic calendar||−388 – −387|
|Ethiopian calendar||−112 – −111|
|- Vikram Samvat||−48 – −47|
|- Shaka Samvat||N/A|
|- Kali Yuga||2996–2997|
|Iranian calendar||726 BP – 725 BP|
|Islamic calendar||748 BH – 747 BH|
|Minguo calendar||2016 before ROC|
|Seleucid era||207/208 AG|
|Thai solar calendar||438–439|
22 or −359 or −1131
— to —
23 or −358 or −1130
Year 105 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Rufus and Maximus (or, less frequently, year 649 Ab urbe condita). The denomination 105 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.
- October 6 – The Battle of Arausio, where the Cimbri destroy two Roman armies on the Rhône, is the most severe defeat of Roman forces since the Battle of Cannae.
- Gaius Marius, together with the consul Publius Rutilius Rufus, initiates sweeping reforms of the Roman army.
- Lucius Cornelius Sulla secures the capture of Jugurtha. His success is made possible by the treachery of Bocchus I, king of Mauretania, and this ends the Jugurthine War (which has begun in 112 BC).
- At Rome, the first official gladiator match is demonstrated by gladiators from Capua, as part of a training program for the military.
- Paper is invented.
- Drusus Claudius Nero I, Roman politician and general
- Marcus Atius Balbus, Roman praetor and governor (d. 51 BC)
- Marcus Aurelius Scaurus, Roman politician and general, executed as a prisoner of war in the advent of the Battle of Arausio
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