The free-to-play multiplayer role-playing game will launch in the early stages of next year for the PC.
"Phantasy Star Online was a revolutionary game when it was released, and we want to make sure that its successor in the series is every bit as ambitious," said Chris Olson, vice president of digital business at SEGA of America.
"We look forward to introducing Phantasy Star Online 2's unique, easy-to-access multiplayer action to the rest of the world next year!"
Comparing the game to table-top RPG experiences, Phantasy Star Online 2 producer Satoshi Sakai promises a quest full of surprises.
"The number one thing we want to provide players in Phantasy Star Online 2 is an adventure that changes every time they log in.
"Just as great table-top RPG experiences revolve around imaginative and unexpected encounters, we want players to consistently be surprised as they explore dungeons and undertake quests."
Phantasy Star Online 2 will be available on PC and PlayStation Vita with cross-platform play, although it's unclear if the handheld version will also be released outside of Japan.
A separate version for smartphones will release later with simplified controls and character creation features.
> Retro Corner: Phantasy Star Online
Watch a gameplay video of Phantasy Star Online 2's Japanese version below: