|Millennium:||1st millennium BC|
|Centuries:||3rd century BC – 2nd century BC – 1st century BC|
|Decades:||130s BC 120s BC 110s BC – 100s BC – 90s BC 80s BC 70s BC|
|Years:||107 BC 106 BC 105 BC – 104 BC – 103 BC 102 BC 101 BC|
|104 BC by topic|
|Gregorian calendar||104 BC|
|Ab urbe condita||650|
|Bahá'í calendar||−1947 – −1946|
|English Regnal year||N/A|
|Chinese calendar||丙子年 (Fire Rat)
2593 or 2533
— to —
丁丑年 (Fire Ox)
2594 or 2534
|Coptic calendar||−387 – −386|
|Ethiopian calendar||−111 – −110|
|- Vikram Samvat||−47 – −46|
|- Shaka Samvat||N/A|
|- Kali Yuga||2998–2999|
|Igbo calendar||−1103 – −1102|
|Iranian calendar||725 BP – 724 BP|
|Islamic calendar||747 BH – 746 BH|
|Minguo calendar||2015 before ROC
|Thai solar calendar||440|
|Wikimedia Commons has media related to 104 BC.|
Year 104 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Marius and Fimbria (or, less frequently, year 650 Ab urbe condita). The denomination 104 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.
- In Rome exist a state of emergency, the way to Italy lays open to the Germanic invaders. Gaius Marius, the conqueror of Jugurtha, is elected consul for the second time. He celebrates his triumph over Jugurtha, who is led in the procession and thrown into the Tullianum where he dies of starvation.
- Second Servile War: Athenion starts a slave rebellion in Segesta (Sicily).
- Emperor Wu of Han maintains large armies of occupation and burdens the Chinese economy. Landowners expanding their holdings, but farmers are forced to borrow at usurious rates and paying 50 percent of their crops as rent. Homelessness and banditry has increased, and agricultural productivity has declined.
- Sima Qian starts writing his Shiji.
- Jugurtha, king of Numidia (execution by Rome) (b. c. 160 BC)
- Dong Zhongshu, Chinese scholar who promoted Confucianism at the central court of the Han Dynasty (b. 179 BC)
- John Hyrcanus, prince (ruler) and high priest of Judea. (b. 164 BC)