The town has very ancient origins. However it is not certain if these are Latin, Volsci or Etruscan. The site was conquered by the Romans during the first Latin war, under Anco Marzio and it appears that this was the time when it took on the name of Velitrae. During the period of conquest, by demonstrating valour and a rare long-sightedness, the town managed to enter into an alliance with Rome, establishing that the Gens Octavia originating from Velitrae, once transferred to Rome at the time of Tarquinio Prisco, would have been able to obtain political rights and Roman citizenship immediately.
Finally under the control of Rome only in 338 B.C., the town became a Municipality and experienced a period of great prosperity. Velitrae became rich, its prestige grew and it became one of the favourite holiday resorts for famous Romans who built splendid villas in the imperial age in Velletri.
One interesting piece of information: it was here that the famous Augustus, a descendent of the Octavia family, originating from Velletri, spent his childhood. The town suffered a great blow in 410 A.D. when it was invaded by Alarico.
However it recovered and established itself as a Commune at the end of the XII century. In the X century Velletri was governed by the Counts of Tusculum, who in that period controlled the Alban Hills and the Agro Romano. During the middle Ages, until 1591, Velletri enjoyed the exceptional condition of free commune of central Italy and managed to preserve its own life as a town.
During the XIV century the town fought against the commune of Rome and in 1500 passed under the direct control of the Church.
In 1798 the town rebelled, recognising the Republic, but just after this it revolted and 900 of its citizens fought against the troops of Gioacchino Murat at Castel Gandolfo. Between 8th September 1943 and 2nd June 1944 Velletri suffered serious damage from massive air raids.