|Millennium:||1st millennium BC|
|87 BC by topic|
|Gregorian calendar||87 BC|
|Ab urbe condita||667|
|Ancient Egypt era||XXXIII dynasty, 237|
|- Pharaoh||Ptolemy IX Lathyros, 2|
|Ancient Greek era||173rd Olympiad, year 2|
|Balinese saka calendar||N/A|
|Chinese calendar||癸巳年 (Water Snake)|
2610 or 2550
— to —
甲午年 (Wood Horse)
2611 or 2551
|Coptic calendar||−370 – −369|
|Ethiopian calendar||−94 – −93|
|- Vikram Samvat||−30 – −29|
|- Shaka Samvat||N/A|
|- Kali Yuga||3014–3015|
|Iranian calendar||708 BP – 707 BP|
|Islamic calendar||730 BH – 729 BH|
|Minguo calendar||1998 before ROC|
|Seleucid era||225/226 AG|
|Thai solar calendar||456–457|
40 or −341 or −1113
— to —
41 or −340 or −1112
Year 87 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Octavius and Cinna/Merula (or, less frequently, year 667 Ab urbe condita). The denomination 87 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.
- Lucius Cornelius Cinna is elected consul of Rome, thus returning the rule of Rome back to the democrats.
- Sulla arrives in Greece and besieges Athens. He orders Lucius Licinius Lucullus to raise a fleet from Rome's allies around the eastern Mediterranean.
- Ostia is razed by Gaius Marius as he comes back from Africa with an army to take Rome by force.
- March 29 – Emperor Han Wudi dies after a 54-year reign in which he leads the Han Dynasty (China) through its greatest expansion, the Empire's borders span from modern Kyrgyzstan in the west, to Korea in the east, and to northern Vietnam in the south.
- Antikythera mechanism manufactured.
- Lucius Munatius Plancus, Roman consul (approximate date)
- March 29 – Han Wudi, emperor of the Han Dynasty (b. 157 BC)
- Apollodorus of Artemita, Greek writer
- Gaius Atilius Serranus, Roman consul and senator
- Gaius Julius Caesar Strabo Vopiscus, Roman consul
- Gnaeus Pompeius Strabo, Roman general and politician (b. 135 BC)
- Gotarzes I, ruler (shah) of the Parthian Empire
- Lucius Cornelius Merula, Roman politician and priest
- Lucius Julius Caesar, Roman consul (killed by partisans of Gaius Marius)
- Marcus Antonius, Roman consul (executed by order of Marius and Cinna)
- Publius Licinius Crassus, Roman consul and censor (killed by Marians invading Rome)
- Quintus Ancharius, Roman politician (executed by order of Marius and Cinna)