Which Assassin's Creed game was the first in the series to feature a fully playable multiplayer mode?

Assassin's Creed: Brotherhood was the first Assassin's Creed game to feature a fully playable multiplayer mode.

Released in 2010, Brotherhood added competitive multiplayer alongside its single-player campaign. Players controlled trained assassins in urban environments, selected targets, and tried to identify and eliminate opponents while avoiding detection themselves.

The multiplayer design emphasized stealth, disguise, timing, and awareness rather than straightforward combat. Players could earn points for cautious approaches and varied assassination methods, reflecting the series' core themes in a competitive format.

Assassin's Creed II had no comparable playable competitive mode, although it established the modern historical framework and Ezio's story. Revelations and Assassin's Creed III later expanded multiplayer features, but they followed Brotherhood. This distinction concerns a fully playable multiplayer component, not online connectivity or downloadable extras.