Arsinoe II was born in Macedonia to King Ptolemy I, the ruler of Lybia and Egypt. In order to make Thrace an ally, Ptolemy married off Arsinoe at age sixteen to Lysimachus, a 45-year-old military leader from the Greek province of Thrace.
For eighteen years, she remained the wife of Lysimachus, and lived in relative comfort in Thrace. She bore three sons to her husband before he died in 281 BC.
Around this same time, her father, Ptolemy also died, and her brother, Ptolemy II took the throne.
Worried that her sons may be in danger because they were heirs to Ptolemy II's throne, she sought the help of her half brother, the Macedonian king Ptolemy Keraunos. He agreed to marry her out of mercy.
To secure her sons' positions as heirs to the Macedonian throne, Arsinoe had had her husband's son murdered. When he retaliated and killed two of her sons, she divorced him and fled to Egypt.
In Egypt, she convinced her brother, Ptolemy II, to leave his wife, Arsinoe I, and marry her. Together, they were very strong rulers, and due to her great skill in foreign affairs, she was responsible for the success of Ptolemy II's campaign against Syria.
In 271 BC, at age 45, Arsinoe died suddenly. After her death, Ptolemy II deified her and issued coins with her portrait. As with other rulers of Egypt, many people worshipped her and somewhat of a cult was formed.
Interestingly enough, after Ptolemy II died, it was her son, not Ptolemy's son (her step-son), that succeeded him in the throne.