The Templars are the rival order opposing the Assassins in Assassin's Creed.
Across the series, the Assassins generally defend free will, while the Templars seek peace through control and centralized authority. This conflict is presented as an ongoing ideological struggle rather than a simple battle between historically identical organizations.
The games often connect their fictional Templars to the real medieval Knights Templar, but the series substantially reimagines the organization. Historical figures, political factions, and modern corporations can all serve the Templars' goals in different periods.
The Assassins and Templars are also called the Hidden Ones and the Order of the Ancients in Assassin's Creed Origins, reflecting earlier forms of the two traditions. Those names describe historical predecessors within the fiction, not separate permanent enemies.