Themistocles is a Classical Era Great Admiral in Civilization VI. His unit provides +5 
Combat Strength and +1 
Movement to Classical and Medieval era naval units within 2 tiles.
Themistocles can be retired to instantly create a Quadrireme unit in standard games, or to grant +2 Loyalty to a city in Rise and Fall. In Gathering Storm, he can be retired to create a Quadrireme and grant +20% 
Production towards Naval Ranged promotion class.
Strategy[]
The weakness of the Quadrireme means that only the Byzantines (who have the Dromon) can take full advantage of Themistocles under the vanilla ruleset. The Loyalty bonus from retiring him under the Rise and Fall ruleset is inconsequential, but the Production bonus toward naval ranged units under the Gathering Storm ruleset makes him useful to civilizations such as Indonesia and Brazil, who have unique units of this class.
Civilopedia entry[]
Themistocles was the savior of Athens – well, perhaps not Athens since the Persians captured and burned it, but of Greece – yet later in life was forced to flee into exile by the Athenians. Born c. 524 BC to the aristocrat Neocles and a non-Athenian concubine, after an unrecorded (and likely unremarkable) childhood Themistocles was elected archon (magistrate) and then Archon Eponymous, the highest office in Athens, a year later in 493 BC. Convinced that the fate of Athens lay with the sea, he initiated the public works that would transform the rocky bays of Piraeus into defensible harbors. Moreover, Themistocles persuaded the citizens that – despite the victory at Marathon – the Persian threat was not over and that Athens must construct a great fleet. Thus, when Xerxes invaded in 480, Athens could float 200 triremes.
Taking command of the combined fleet, Themistocles fought the massive Persian navy (reportedly over 1200 ships) to a draw in the bloody three-day skirmish at Artemisium. Even as the Persians rolled over the Spartans and Thespians at Thermopylae and advanced on Athens, Themistocles lured the Persian fleet into the narrow confines of the Straits at Salamis. There – in one of the greatest naval victories of civilization – Themistocles dealt the Persians a decisive defeat. Eventually, unable to supply the land troops, the Persians withdrew, never to threaten the city-states of Greece again.
But while Sparta and others honored Themistocles with ovations and monuments, in his own Athens he was ostracized thanks to political intrigue (so much for democracy), rumors of collusion with Xerxes, and his own self-serving arrogance. To save his life, Themistocles fled, spending his last years as governor in several city-states still subject to Xerxes. He died in Magnesia in 459 BC.
