20 BC

Year 20 BC was either a common year starting on Wednesday or Thursday or a leap year starting on Tuesday, Wednesday or Thursday of the Julian calendar. At the time, it was known as the Year of the Consulship of Appuleius and Nerva.

 Events 
 Rome and Parthia make a peace treaty
 King Herod the Great begins to renovate the Temple in Jerusalem
 Maison Carrée, Nîmes, France, is built (approximate date)
 Marcus Verrius Flaccus' dictionary De verborum significatu is published. It is one of the first great dictionaries in history.
 Shakas no longer control northwest India

 Births 

 Gaius Caesar, grandson of Augustus Caesar (d. AD 4)
 Philo, the philosopher (approximate date) (d. AD 50)