Which historical brotherhood is the Order of the Ancients renamed as in Assassin's Creed Origins?

In Assassin's Creed Origins, the Order of the Ancients is the precursor to the Order of the Knights Templar.

The Order of the Ancients is a secret organization operating across the ancient Mediterranean world. Its members seek political control and influence, placing them in opposition to Bayek and Aya as they establish the Hidden Ones.

The series presents the later Templar Order as developing from this earlier organization. The connection is part of Assassin's Creed's fictional historical mythology rather than a claim that the game depicts the exact real-world founding process of the medieval Knights Templar.

The Hidden Ones, founded by Bayek and Aya, are likewise presented as the predecessors of the Assassin Brotherhood. The Cult of Kosmos belongs to Assassin's Creed Odyssey, making it a related but separate faction.