Which Assassin's Creed game is set mainly during the Golden Age of Piracy?

Assassin's Creed IV: Black Flag is the Assassin's Creed game set mainly during the Golden Age of Piracy.

Released in 2013, Black Flag follows Edward Kenway, a Welsh privateer who becomes involved with both the Assassins and the Templars in the early eighteenth-century Caribbean. The game emphasizes naval exploration, ship combat, boarding actions and visits to islands and port cities.

Edward is the grandfather of Connor Kenway, the protagonist of Assassin's Creed III. This makes Black Flag a prequel in the Kenway family line, although it was released after Assassin's Creed III. Edward's ship is the Jackdaw, which players upgrade throughout the campaign.

The game also includes a modern-day storyline at Abstergo Entertainment. Its Caribbean setting is broader and more maritime than the colonial North American setting of Assassin's Creed III, a common source of confusion between the two titles.