| Millennium: | 1st millennium BC |
|---|---|
| Centuries: | 2nd century BC – 1st century BC – 1st century |
| Decades: | 120s BC 110s BC 100s BC – 90s BC – 80s BC 70s BC 60s BC |
| Years: | 94 BC 93 BC 92 BC – 91 BC – 90 BC 89 BC 88 BC |
| 91 BC by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishments and disestablishments categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 91 BC |
| Ab urbe condita | 663 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1934 – -1933 |
| Bengali calendar | -683 |
| Berber calendar | 860 |
| Buddhist calendar | 454 |
| Burmese calendar | -728 |
| Byzantine calendar | 5418 – 5419 |
| Chinese calendar | [[Sexagenary cycle|]]年 (2546/2606) — to —
[[Sexagenary cycle|]]年(2547/2607) |
| Coptic calendar | -374 – -373 |
| Ethiopian calendar | -98 – -97 |
| Hebrew calendar | 3670 – 3671 |
| Hindu calendars | |
| - Bikram Samwat | -34 – -33 |
| - Shaka Samvat | N/A |
| - Kali Yuga | 3011 – 3012 |
| Holocene calendar | 9910 |
| Iranian calendar | 712 BP – 711 BP |
| Islamic calendar | 734 BH – 733 BH |
| Japanese calendar | |
| Korean calendar | 2243 |
| Thai solar calendar | 453 |
Year 91 BC was a year of the pre-Julian calendar.