The siege of Jerusalem in the year 70 CE was the decisive event of the First Jewish–Roman War, in which the Roman army captured the city of Jerusalem and destroyed both the city and its Temple. The Roman army, led by the future Emperor Titus, with Tiberius Julius Alexander as his second-in-command, besieged and conquered the city of Jerusalem, which had been controlled by Judean rebel factions since 66 CE, following the Jerusalem riots of 66, when the Judean provisional government was formed in Jerusalem.

The siege of the city began on 14 April 70 CE, three days before the beginning of Passover that year. The Jews enjoyed some minor victories, one highpoint being when sappers from Adiabene managed to tunnel under the city and set bitumen fires in the tunnels, which collapsed with the Roman siege engines falling into the crevices.The siege lasted for about five months; it ended in August 70 CE on Tisha B'Av with the burning and destruction of the Second Temple. The Romans then entered and sacked the Lower City. The Arch of Titus, celebrating the Roman sack of Jerusalem and the Temple, still stands in Rome. The conquest of the city was complete on approximately 8 September 70 CE.

Josephus places the siege in the second year of Vespasian, which corresponds to year 70 of the Common Era.