The new series instalment was seemingly leaked via marketing materials this week, which showed a hooded figure surrounded by pirates.
According to an Examiner report, the game's main character is Edward Kenway, father of Haytham Kenway from Assassin's Creed 3, and an Assassin and known Privateer.
Black Flag is claimed to be set during 1715 in the Caribbean, with Jamaica, Cuba and the Bahamas among the islands that will be visited.
Weeks ago a Reddit poster who claimed to have seen promotional materials for the game said Black Flag would carry a strong focus on naval combat.
It is claimed that the game is up and running on Xbox 360, but next-generation versions are also planned.
Ubisoft CEO Yves Guillemot confirmed earlier this month that the company plans to publish a new Assassin's Creed game during the 2014 financial year (by April 2014).