The Hidden Ones are the organization that precedes the Assassins in Assassin's Creed Origins.
Bayek and Aya establish the Hidden Ones near the end of the game after confronting the Order of the Ancients. The organization is presented as the early form of the Assassin Brotherhood, adopting principles that later define the Assassins, including resisting tyranny and protecting ordinary people from those who abuse power.
Origins is set in the first century BCE, and its story explains how the Hidden Ones begin operating secretly. The group uses hidden blades, concealed bureaus, and a creed-like philosophy, but the familiar name “Assassins” is not yet the organization's official title in this period.
The Order of the Ancients is the opposing organization in Origins and is an early predecessor of the Templars. The distinction matters because the game shows both sides before their later medieval identities fully develop.