Gylon, also known as Gylon of Cerameis, was a Greek military official and the maternal grandfather of Demosthenes. He is known for his role in the capture and ultimately turning over of Nymphaeum to the Bosporans, for which he was punished.
Nymphaeum came under Athenian rule, when Gylon captured the city and established a garrison there, along the strategic route of the grain. Until that time, the city was under the influence of the Scythians. He lived in Ancient Crimea the Bosporan Kingdom. Gylon said that he had betrayed Nymphaeum to the "enemy", when in 405 BC, He handed it to the Bosporan king Satyros in exchange for the necessary grain. One theory is that it was no longer possible for the Athenians to support the Outpost. but Glyon were punished for their role in releasing Nyphaeum. He was first sentenced to death, but the punishment was later changed to the fine, which Demosthenes paid.
Gylon, married a woman of nobility from Scythia. They had a daughter, Cleobule who married Demosthenes senior and they had a son Demosthenes.