Laodice I was the first wife, and likely the cousin, of Antiochus II Theos of the Seleucid dynasty. 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'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 Antiochus himself died immediately thereafter (she is said to have poisoned him). Berenice's son was less than four years old; Laodice's eldest son rose in rebellion, in the Laodicean War; Laodice is said to have raised troops in Anatolia for this war. Ptolemy III, brother of Berenice, invaded Syria, and took Antioch, but Laodice and her sons were killed.

Laodice's son reigned as Seleucus Callinicus, whom modern historians number Seleucus II.