Phantasy Star Online is an online role-playing game (RPG) developed by Sonic Team and published by Sega in 2000 for the Dreamcast. Following Sega's exit from the console business in 2001, the game was ported to GameCube and Xbox as Episode I & II, featuring new characters, environments and other features. It was the first online RPG for game consoles; players adventure with up to three others over the internet to complete quests, collect items, and fight enemies in real-time action RPG combat. The story is unrelated to previous games in the Phantasy Star series.

Phantasy Star Online is an action role-playing game primarily played with other players cooperatively over the internet. Players take on the role of adventurers sent to explore Ragol, an uncharted planet. To create their character, they choose between a handful of races and classes, which define their abilities and statistics; for example, some types are better with "techniques" (magic spells) while others are more skilled with ranged or melee weapons.

Players can play either online or offline. Online, players are brought to a lobby where they can chat and organize teams of up to four. Team members can communicate by typing using a physical or onscreen keyboard, even when in different environments.[ Preset phrases are automatically translated between languages, and custom emoticons are also supported. Players can also exchange "guild cards" to exchange private messages and see when the other is online.