Eleazar ben Simon is a Zealot leader during the First Jewish-Roman War who fights against the armies of Cestius Gallus, Vespasian, and Titus Flavius.

From the onset of the war in 66 CE until the destruction of the temple in 70 CE, he fights vehemently against the Roman garrisons in Judea and against his fellow Jewish political opponents in order to establish an independent Jewish state at Jerusalem.

Although the Jewish defeat at Jerusalem cannot be entirely attributed to Eleazar ben Simon, his inability to establish unity with John of Gischala and Simon bar Giora results in a bitter civil war that weakens the Jewish resistance against Rome.

Eleazar ben Simon and his Zealots' radical anti-Roman policies and eradication of the moderate temple aristocracy from Jerusalem in 67 CE also prevents any peaceful agreement with Rome to avoid the death and destruction thatr ensues in 70 CE.