At which event was StarCraft II first publicly announced?

StarCraft II was first publicly announced at the Blizzard Worldwide Invitational 2007.

Blizzard revealed the sequel in Seoul, South Korea, on May 19, 2007. The announcement included a cinematic presentation and gameplay footage, confirming that the company was developing a full real-time strategy follow-up to StarCraft and Brood War.

The location was significant because South Korea had become the center of professional StarCraft competition. The original game had a large player base there, and televised tournaments had made its top competitors widely known. Announcing the sequel in Seoul connected the new game directly with that established community.

The event is sometimes confused with BlizzCon, Blizzard’s own convention in the United States. BlizzCon later hosted extensive StarCraft II demonstrations and announcements, but it was not the venue where the game was first revealed publicly. StarCraft II ultimately launched as three campaign installments beginning with Wings of Liberty in 2010.