Pharnaces I (; lived 2nd century BC), fifth king of Pontus and was of Persian and Greek Macedonian ancestry. He was the son of King Mithridates III of Pontus and his wife Laodice, whom he succeeded on the throne. Pharnaces had two siblings: a brother called Mithridates IV of Pontus and a sister called Laodice who succeeded as Pontian monarchs on the throne. He was born and raised in the Kingdom of Pontus.