The Hasideans (Hebrew: חסידים הראשונים, Hasidim ha-Rishonim, Greek Ἀσιδαῖοι or Asidaioi, also transcribed as Hasidaeans and Assideans) were a Jewish group during the Maccabean Revolt that took place from around 167–142 BCE. The Hasideans are mentioned three times in the books of the Maccabees, the main contemporary sources from the period. According to the book 1 Maccabees, during the early phases of the anti-Jewish decrees and persecution proclaimed by King Antiochus IV Epiphanes, some Hasideans joined up with Mattathias the Hasmonean as he martialed forces and allies for his rebellion (~167–166 BCE). Later on, during the term of High Priest Alcimus, some Hasideans apparently trusted Alcimus's promises at first and attempted to negotiate a settlement with the government, but were betrayed and executed (~161 BCE). In the book 2 Maccabees, Judas Maccabeus is described as the leader of the Hasideans and of them all as troublemakers disrupting the peace, but by Alcimus, a source the book considers untrustworthy and corrupt.
The Hasideans have been the object of much scholarly speculation: were they a specific group with a coherent ideology, or merely a generic term for "the faithful"? If they were a group, what was their religious and political stance? What happened to them after the Maccabean Revolt concluded? Were they predecessors of the Pharisees, the Essenes, both, or neither? Scholars have come to different conclusions: from seeing them as religious "moderates" whose main goal was the preservation of traditionalist Judaism against Hellenism (but not necessarily for establishing a separate independent political state) to seeing them as simply as a very religious group who were betrayed.