The Ancients (in their own tongue Anquietas) are a fictional humanoid race in the Stargate franchise. They are called by this name in the Milky Way galaxy, and the Ancestors and Lanteans in the Pegasus galaxy. The Ancients are one of two groups of the Alterans; the other being the Ori, the main antagonists in the later seasons of Stargate SG-1. In the Stargate universe, the Ancients are one of the most technologically advanced species known to have existed. The Ancients evolved tens of millions of years ago and reached advanced level of technology long before humans evolved on Earth. They lived in the Milky Way and Pegasus galaxies prior to their ascension. The Ancients might be best known as the ones who constructed the Stargates; big ring-shaped gates allowing wormhole travel. The Stargates are commonly used by Earth humans, Goa'ulds and Wraiths as seen in the Stargate TV-series to travel and explore Milky Way and Pegasus.
Millions of years ago, the first evolution of humanity known as the Alterans (from Latin alteri, "the others", though in canon, it descends from the Ancient's own language), lived in a distant unknown galaxy while proceeding along the evolutionary path to ascension. At the time, those who were later to be known as the Ori and the Ancients were not distinguished from each other, and lived in one society. However, a philosophical division emerged. Over time, the Ori grew more and more fervent in their religious belief, while the Ancients adopted a more scientific outlook. Ultimately, their viewpoints diverged so much that the two groups split apart and began to oppose each other, culminating in the Ori attempting to destroy the Ancients. Instead of going to war, the Ancients decided to leave their galaxy, and began searching for a new home. The Ori later used their departure to their advantage, including their departure in the Book of Origin, claiming that the mountain the Ancients leveled while leaving contained evil and that it was buried as the mountain collapsed.