Year 80 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Sulla and Metellus Pius (or, less frequently, year 674 Ab urbe condita). The denomination 80 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.

• Quintus Sertorius re-enters Iberia with a tiny army (2,600 men) and opens a successful campaign against the Sullan forces.
• Battle of the Baetis River: A force of Populares exiles under Sertorius defeat the legal Roman army of Lucius Fulfidias in Hispania, starting the Sertorian War; Quintus Caecilius Metellus Pius takes command on behalf of Sulla.
• Pompeii becomes the Roman colony Colonia Cornelia Veneria Pompei when Sulla occupies the city with at least 4,000 soldier-colonizers.^[1]

• Ptolemy XII Auletes succeeds Ptolemy XI Alexander II to the throne of Egypt.
• Ptolemy XI marries Berenice III, but murders his bride for unknown reasons.
• Alexandria comes under Roman jurisdiction.

• Roman artists begin to extend the space of a room visually with painted scenes of figures on a shallow stage or with a landscape or cityscape.

• Meleager publishes his Garland, the earliest known anthology of Greek poetry.

• Scribonia, wife to the Roman Emperor Augustus (approximate date) (d. AD 16)

• Berenice III, queen regnant of Egypt (b. 120 BC)
• Caecilia Metella Dalmatica, daughter of Lucius Caecilius Metellus Dalmaticus (approximate date)
• Lucius Cornelius Chrysogonus, Greek freedman
• Ptolemy XI Alexander II, king (pharaoh) of Egypt
• Sang Hongyang, Chinese politician of the Han dynasty
• Shangguan Jie, Chinese politician of the Han dynasty
• Princess Eyi, Han Chinese princess