Year 73 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Lucullus and Longinus (or, less frequently, year 681 Ab urbe condita). The denomination 73 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.

• Third Servile War: Spartacus, a Thracian gladiator, escapes with around 70 slave-gladiators from a gladiator school at Capua. They defeat a small Roman force and equip themselves with captured military equipment as well with gladiatorial weapons. Spartacus and his band of gladiators plunder the region surrounding Capua and retire to a defensible position on Mount Vesuvius.^[1]
• Battle of Mount Vesuvius: Spartacus defeats a Roman militia force (3,000 men) under Gaius Claudius Glaber. The rebel slaves spend the winter of 73–72 BC training, arming and equipping their new recruits, as well as expanding their raiding territory, which includes the towns of Nola, Nuceria, Thurii and Metapontum.
• On the Iberian Peninsula (part of the Roman Republic) rebel leader Quintus Sertorius is assassinated by some of his own lieutenants (lead by Marcus Perperna).^[a] Perperna takes command of the rebel army.

• Herod the Great, client king of Judea (d. 4 BC)^[2]
• Marcus Porcius Cato, assassin of Julius Caesar (d. 42 BC)

• Devabhuti, king of the Shunga Empire
• Gaius Aurelius Cotta, Roman statesman and orator
• Quintus Sertorius, leader of the Sertorian rebels during the Sertorian War
• Heli, king of Britain (approximate date)