| Millennium: | 1st millennium BC |
|---|---|
| Centuries: | 2nd century BC – 1st century BC – 1st century |
| Decades: | 130s BC 120s BC 110s BC – 100s BC – 90s BC 80s BC 70s BC |
| Years: | 103 BC 102 BC 101 BC – 100 BC – 99 BC 98 BC 97 BC |
| 100 BC by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishments and disestablishments categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 100 BC |
| Ab urbe condita | 654 |
| Armenian calendar | N/A |
| Assyrian calendar | 4651 |
| Bahá'í calendar | -1943–-1942 |
| Bengali calendar | -692 |
| Berber calendar | 851 |
| English Regnal year | N/A |
| Buddhist calendar | 445 |
| Burmese calendar | -737 |
| Byzantine calendar | 5409–5410 |
| Chinese calendar | 庚辰年 (2537/2597) — to —
辛巳年(2538/2598) |
| Coptic calendar | -383–-382 |
| Ethiopian calendar | -107–-106 |
| Hebrew calendar | 3661–3662 |
| Hindu calendars | |
| - Vikram Samvat | -43–-42 |
| - Shaka Samvat | N/A |
| - Kali Yuga | 3002–3003 |
| Holocene calendar | 9901 |
| Iranian calendar | 721 BP – 720 BP |
| Islamic calendar | 743 BH – 742 BH |
| Japanese calendar | |
| Korean calendar | 2234 |
| Minguo calendar | 2011 before ROC 民前2011年 |
| Thai solar calendar | 444 |
Year 100 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 Flaccus (or, less frequently, year 654 Ab urbe condita). The denomination 100 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.