Gylippus was a Spartan general of the 5th century BC; he was the son of Cleandridas, who had been expelled from Sparta for accepting Athenian bribes in 446 BC and had settled at Thurii. His mother may have been a helot. When Alcibiades urged the Spartans to send a general to lead the Syracusan resistance against the Athenian expedition, Gylippus was appointed (414 BC), and his arrival was a turning point of the struggle.

Diodorus, probably following Timaeus, represents him as inducing the Syracusans to pass sentence of death on the captive Athenian generals, but there is also the statement of Philistus (Plutarch, Nicias, 28), a Syracusan who himself took part in the defence, and Thucydides (vii. 86), that he tried, though without success, to save their lives, wishing to take them to Sparta as a signal proof of his success.

Gylippus, like his father, met his downfall in a financial scandal; entrusted by Lysander with an immense sum which he was to deliver to the ephors at Sparta, he could not resist the temptation to enrich himself and, on discovery, went into exile, having been condemned to death in his absence.