Socrates Chrestus (Greek: Σωκράτης ό Χρηστός; Chrestus means "the Good"; died 90–88 BC) was a Greek prince and King of Bithynia.
Socrates was the second son born to the Monarchs Nysa and Nicomedes III of Bithynia. He had a sister called Nysa and his eldest brother was his father’s heir Nicomedes IV of Bithynia. He was born and raised in Bithynia and his mother's maternal uncle was King Mithridates VI of Pontus.
Socrates was a popular prince with the citizens of Bithynia. He received the surname Chrestus because he was peaceful and lamented in his personality.
The father of Socrates, Nicomedes III, died in c. 94 BC and his brother became King, as Nicomedes IV . The first few years of his rule of Nicomedes IV were relatively peaceful. Socrates unfortunately fell under the evil influence of Mithridates VI, who persuaded him to assert his claim to the throne. Mithridates VI sent an assassin named Alexander to murder Nicomedes IV, but his plot failed.
Mithridates VI formed an alliance with Socrates. As a part of the alliance, Mithridates VI betrothed or married Socrates to his daughter Orsabaris, thus maintaining indirect control of the Kingdom of Bithynia.
Then Mithridates VI gave Socrates command of a Pontic army and he invaded Bithynia with the support of Mithridates and his army. As Socrates marched across the countryside of Bithynia, he eventually approached the capital, Nicomedia, where Nicomedes IV barricaded himself inside his castle.
Socrates with the Pontian army defeated the army of Nicomedes IV, who was forced to flee to Italy. Socrates became King of Bithynia and probably assumed the name Memnon Nicomedes, by which he is also known. Nicomedes IV with the support of the Roman Senate declared war against Socrates, eventually winning a military victory and thanks to Rome’s influence in the region being restored to the Bithynian throne as King in 90 BC.