Arsinoe III of Egypt

Arsinoe III was the daughter of Ptolemy III Euergetes and Berenice II, who ruled Egypt from 246 to 221 BC. She married her younger brother, Ptolemy IV Philopator, in 220 BC, and became his co-ruler and consort. She was a popular and influential queen, who took an active part in the government and military affairs of the country. She accompanied her husband to the Battle of Raphia in 217 BC, where they defeated the Seleucid king Antiochus III. She also encouraged the Egyptian troops before the battle and promised them rewards for their victory. She gave birth to a son, Ptolemy V, around 210 BC, who succeeded his father after his death in 205 BC. Arsinoe III was murdered by the royal ministers, Agathocles and Sosibius, who feared her power and popularity. They kept her death secret until they secured the regency for themselves. Her death caused riots among the people, who loved and respected her. She was the last of the Ptolemaic queens to wield any political influence. She was also the subject of a lost manuscript by the famous mathematician and astronomer Eratosthenes, who wrote a memoir of her life and achievements.