Laodice I

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Laodice I was the first wife, and likely the cousin, of Antiochus II Theos of the Seleucid Empire. He repudiated her and her children, when (as part of a peace treaty with Ptolemy II Philadelphus of Egypt in 250 BC) he agreed to marry Berenice, Ptolemy II's daughter; and declared his eldest son by Berenice his heir.

According to Eusebius, Laodice I was a daughter of Achaeus, probably the same as the father of Antiochis, who was mother of Attalus I, king of Pergamus. When Ptolemy died in 246 BC, Antiochus took Laodice back but died immediately thereafter (she is said to have poisoned him). Berenice's son was less than four years old, and Laodice argued that her eldest son, Seleucus, had been named heir to the throne by Antiochus on his deathbed. Laodice had Berenice and her son murdered, which began the Third Syrian War (also known as the Laodicean War) between the newly crowned Seleucus and Ptolemy III of Egypt, Berenice's brother.

During the course of this war, Laodice attempted to take control over the Empire by insisting that Seleucus make his younger brother Antiochus Hierax co-regent and give him all Seleucid territory in Anatolia. Antiochus promptly declared independence and began fighting a war with his brother. This disunity undermined Seleucus' ability to fight the war, and he lost in 241 BC. There is no little information regarding Laodice's death, but she seems to have died before 236 BC.