Assassin's Creed IV: Black Flag is an action-adventure video game developed by Ubisoft Montreal and published by Ubisoft. It is the sixth major installment in the Assassin's Creed series. Its historical timeframe precedes that of Assassin's Creed III (2012), though its modern-day sequences succeed III's own. Black Flag was first released for PlayStation 3, Xbox 360, and Wii U in October 2013 and a month later for PlayStation 4, Xbox One, and Microsoft Windows. It was released on the Nintendo Switch as part of Assassin's Creed: The Rebel Collection alongside Assassin's Creed Rogue in December 2019.
The plot is set in a fictional history of real-world events and follows the centuries-old struggle between the Assassins, who fight for peace with free will, and the Templars, who desire peace through control. The framing story is set in the 21st century and describes the player as an Abstergo agent. The main story is set in the 18th century Caribbean during the Golden Age of Piracy, and follows notorious Welsh pirate Edward Kenway, grandfather and father of Assassin's Creed III protagonist Ratonhnhaké:ton and antagonist Haytham Kenway, respectively, who stumbles upon the Assassin/Templar conflict. The attempted establishment of a Republic of Pirates utopia (free from either British or Spanish rule) is a significant plot element.
Unlike previous games, gameplay elements focus more on the ship-based exploration of the seamless open world map, while also retaining the series' third-person land-based exploration, melee combat, and stealth system. Multiplayer also returns, albeit with only land-based modes and settings. The game's setting spans the West Indies with the three main cities of Havana, Nassau, and Kingston, along with numerous islands, sunken ships, and forts. Players have the option to harpoon large sea animals and hunt land animals. For the first time in the series, naval exploration is a major part of an Assassin's Creed game, where Edward Kenway captains the Jackdaw, a brig he captures from a Spanish fleet in an early game mission.
Assassin's Creed IV: Black Flag received positive reviews and was one of the best-selling games of 2013, with over 15 million copies sold as of 2020. Critics praised the massive open world gameplay, numerous side-quests, graphics, and improved naval combat. The light-hearted pirate theme and engaging story were well received by critics. The modern-day story, however, received a slightly more mixed response, while criticism fell on aspects of the historical story missions which were considered repetitive. The game received several awards and nominations, including winning the Spike VGX 2013 award for Best Action Adventure Game. It was followed by Assassin's Creed Rogue and Assassin's Creed Unity in November 2014.