In 66 AD, a group of 960 Jewish Zealots decided they would prefer to commit suicide rather than yield to Roman conquest at Masada:

Masada (‘Metsada’ in Hebrew) is the name of the mountain on which the Masada fortress was built. It is more like a plateau or a table mountain, and quite isolated from its surroundings, as there is only one narrow, winding pathway leading up, fittingly called “the Snake.” According to Josephus Flavius, an ancient historian and the only one to record what happened on Masada, Masada was first built by the Hasmoneans, a Jewish dynasty who ruled Judaea in the years between 140-37 BC. Then, between 37-31 BC, King Herod the Great built two palaces there and further fortified the place as a refuge for himself in case of a revolt. However, it proved to be a refuge for Jewish rebels about 90 years later.

A group of Jewish extremists went to Masada after the destruction of the Second Temple. In response, the Roman governor of Judea conducted a siege there and the Jews tried to hold them off, but finally realized that they would lose. Technically, what they committed was not suicide, which is forbidden by Jewish law; instead, the people drew lots, taking turns in killing each other, so that only one person actually killed himself.