Betar (Hebrew: בֵּיתַּר, romanized: Bēttar) was an ancient Jewish town in the Judaean Mountains, continuously inhabited since the Iron Age and up until the 2nd century CE. It is most famously known as the final stronghold of the Bar Kokhba revolt. It was besieged and destroyed by the Romans in 135 CE.
Betar appears in various ancient sources, including the Jerusalem and Babylonian Talmuds, as well as in midrashic literature and Patristic writings. These accounts depict the siege as a prolonged and devastating campaign, culminating in the large-scale massacre of its inhabitants. According to Jewish tradition, tens of thousands were killed, and their bodies were left unburied until the reign of Emperor Antoninus Pius, when burial was finally permitted. The fall of Betar is observed on the fast day of Tisha B'Av, alongside other national calamities such as the destruction of the First and Second Temples in Jerusalem.