Herodias (Greek: Ἡρῳδιάς, Hērǭdiás; c. 15 BC – after AD 39) was a princess of the Herodian dynasty of Judaea during the time of the Roman Empire. Christian writings connect her with John the Baptist's execution.
Herod the Great executed his sons, Alexander and Aristobulus IV, in 7 BC, and engaged Herodias to Herod II (born ca. 27 BC; died AD 33), her half-uncle. The marriage was opposed by Antipater II, Herod the Great's eldest son, and so Herod demoted Herod II to second in line to the throne. Antipater's execution in 4 BC for plotting to poison his father left Herod II as first in line, but his mother's knowledge of the poison plot, and failure to stop it, led to his being dropped from this position in Herod I's will just days before he died.
Both the Gospel of Matthew and Gospel of Mark state that Herodias was married to Philip, therefore some scholars have argued his name was "Herod Philip" (not to be confused with Philip the Tetrarch, whom some writers call Herod Philip II). Many scholars dispute this, however, and believe it was an error, a theory supported by the fact that the Gospel of Luke drops the name Philip. Because he was the grandson of the high priest Simon Boethus he is sometimes described as Herod Boethus, but there is no evidence he was called by that name.
There was one daughter from this marriage, Salome. Herodias later divorced Herod II, although it is unclear when they were divorced. According to the historian Josephus:
Herodias took upon her to confound the laws of our country, and divorced herself from her husband while he was alive, and was married to Herod Antipas
Herodias' second husband was Herod Antipas (born before 20 BC; died after 39 AD) half-brother of Herod II (her first husband). He is best known today for his role in events that led to the executions of John the Baptist and Jesus of Nazareth.
Antipas divorced his first wife Phasaelis, the daughter of King Aretas IV of Nabatea, in favor of Herodias. According to biblical scholars, the Gospel of Matthew and the Gospel of Luke, it was this proposed marriage which John the Baptist publicly criticized. Aside from provoking his conflict with the Baptist, the tetrarch's divorce added a personal grievance to previous disputes with Aretas over territory on the border of Perea and Nabatea. Aretas sent an army to punish Antipas, and was joined in this endeavor by auxiliary troops from the province of Syria. Josephus calls these troops 'fugitives', while Moses of Chorene says they were the army of King Abgarus V of Edessa, under the command of commander Khosran Ardzrouni. 
The result of this war proved disastrous for Antipas; a Roman counter-offensive was ordered by Tiberius, but abandoned upon that emperor's death in 37 AD. In 39 AD Antipas was accused by his nephew/brother-in-law Agrippa I of conspiracy against the new Roman emperor Caligula, who sent him into exile in Gaul. Accompanied there by Herodias, he died at an unknown date. It is uncertain if Herodias had any children by her second husband, Herod Antipas.
In the Gospels of Matthew and Mark, Herodias plays a major role in John the Baptist's execution, using her daughter's dance before Antipas and his party guests to ask for the head of the Baptist as a reward. According to the Gospel of Mark, Antipas did not want to put John the Baptist to death, for Antipas liked to listen to John the Baptist preach (Mark 6:20). Furthermore, Antipas may have feared that if John the Baptist were to be put to death, his followers would riot. The Gospel of Luke amplifies the role of Herod by omitting these details.
Some biblical scholars have questioned whether the Gospels give historically accurate accounts of John the Baptist's execution. Some exegetes believe that Antipas' struggle with John the Baptist as told in the Gospels was some kind of a remembrance of the political and religious fight opposing the Israelite monarchs Ahab and Jezebel to the prophet Elijah.
Main article: Aradia
In medieval Europe a widespread belief held Herodias to be the supernatural leader of a supposed cult of witches, synonymous with Diana, Holda and Abundia.
Together with Salome, Herodias was a frequent subject in depictions of the Power of Women topos in the later Medieval and Renaissance periods. The most common moment shown including Herodias is the Feast of Herod, showing Salome presenting John's severed head on a platter as Herodias dines with her husband and others