|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:||101 BC 100 BC 99 BC – 98 BC – 97 BC 96 BC 95 BC|
|98 BC by topic|
|Gregorian calendar||98 BC|
|Ab urbe condita||656|
|Ancient Egypt era||XXXIII dynasty, 226|
|- Pharaoh||Ptolemy X Alexander, 10|
|Ancient Greek era||170th Olympiad, year 3|
|Chinese calendar||壬午年 (Water Horse)
2599 or 2539
— to —
癸未年 (Water Goat)
2600 or 2540
|Coptic calendar||−381 – −380|
|Ethiopian calendar||−105 – −104|
|- Vikram Samvat||−41 – −40|
|- Shaka Samvat||N/A|
|- Kali Yuga||3004–3005|
|Iranian calendar||719 BP – 718 BP|
|Islamic calendar||741 BH – 740 BH|
|Minguo calendar||2009 before ROC
|Seleucid era||214/215 AG|
|Thai solar calendar||445–446|
|Wikimedia Commons has media related to 98 BC.|
Year 98 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Nepos and Didius (or, less frequently, year 656 Ab urbe condita). The denomination 98 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.
- Consuls: Quintus Caecilius Metellus Nepos and Titus Didius
- The Roman Senate passes a resolution forbidding human sacrifice.
- The Senate passes the Lex Caecilia Didia which bans omnibus bills.
- Nigidius Figulus, Roman philosopher (probable date) (d. 45 BC)
- Terentia, first wife of Cicero (d. AD 4).