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) and the Third Year of Tianhan. 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 Senate passes the Lex Caecilia Didia which bans omnibus bills.

• Emperor Wu of Han sends the Han general Gongsun Ao on a mission to rescue general Li Ling from Xiongnu captivity. Gongsun achieves little but receives incorrect information that Li has been training Xiongnu soldiers. Enraged, Emperor Wu exterminates Li's clan.^[1]

• Nigidius Figulus, Roman philosopher (probable date) (d. 45 BC)
• Terentia, first wife of Cicero (d. AD 4).

• Emperor Kaika of Japan, according to legend.