What is the name of the Assassin organization opposing the Templars in the Assassin's Creed series?

The Brotherhood of Assassins is the organization opposing the Templars in the Assassin's Creed series.

The Brotherhood is a secretive group that fights to protect free will. Its members generally oppose the Templars, who seek order and control through powerful artifacts and political influence. The series presents both factions as evolving organizations rather than simple historical armies.

Different eras use different names and structures. In Assassin's Creed Origins, Bayek and Aya establish the Hidden Ones, an early form of the organization. Later games show the Brotherhood operating under names and traditions that develop across centuries.

The term Assassin comes from the historical Nizari Ismaili community, although the games combine historical inspiration with fictional mythology. The Brotherhood's creed emphasizes staying hidden, avoiding harm to innocents, and preserving freedom of choice.