Simon Maccabeus (also referred to as Simon Thassi, Hebrew: שמעון התרסי; died 135 BCE) was the second son of Mattathias and thus a member of the Hasmonean family. Though the name "Thassi" has a connotation of "the Wise", "the Director", "the Guide", "the Man of Counsel", and "the Zealous" are all possible meanings of the term.
He took a prominent part in the Jewish revolt against the Seleucid Empire led by his brothers, Judas Maccabaeus and Jonathan Maccabaeus. The successes of the Jews rendered it expedient for the pretenders to the throne of Syria to show them special favor, and therefore Antiochus VI. appointed Simon strategus, or military commander, of the coast region from the Ladder of Tyre to Egypt. As strategus Simon conquered the cities of Beth-zur and Joppa, garrisoning them with Jewish troops, and built the fortress of Adida in the plain
After the capture of Jonathan, Simon was elected leader by the people, assembled at Jerusalem; he at once completed the fortification of the capital, and made Joppa secure by expelling its Gentile inhabitants and filling it with Jews (I Macc. xiii. 8, 10, 11; "Ant." xiii. 6, § 4). At Hadid he blocked the advance of the treacherous Trypho, who was attempting to enter the country and seize the throne of Syria. Since Trypho could gain nothing by force, he demanded a ransom for Jonathan and the surrender of Jonathan's sons as hostages. Although Simon was fully aware that Trypho would deceive him, he acceded to both demands, so that the people might see that he had done everything possible for his brother. Jonathan was nevertheless treacherously assassinated, and the hostages were not returned. Simon thus became the sole leader of the people.
As the opponent of Trypho, Simon had every reason to side with Demetrius II., to whom he sent a deputation requesting freedom from taxation for the country. The fact that his request was granted implied the recognition of the political independence of Judea.
He became the first prince of the Hebrew Hasmonean Dynasty. He reigned from 142 to 135 BCE.
The Hasmonean Dynasty was founded by a resolution, adopted in 141 BCE, at a large assembly "of the priests and the people and of the elders of the land, to the effect that Simon should be their leader and high priest forever, until there should arise a faithful prophet" (1 Maccabees 14:41).