Giza is the Egyptian region containing the Great Sphinx and the pyramids of Giza in Assassin's Creed Origins.
The game is set in ancient Egypt during the first century BCE and allows players to explore a large representation of the country. Giza is one of its most recognizable areas because it includes the Great Pyramid, other major pyramids, and the Great Sphinx.
Assassin's Creed Origins begins in the Siwa Oasis, where protagonist Bayek serves as a Medjay. The story later takes him through locations including Alexandria, Memphis, and Giza. This distinction matters because Alexandria is another major Egyptian setting, but it does not contain the famous Giza pyramid complex.
The game combines archaeological landmarks with a fictional origin story for the Hidden Ones, the organization that later becomes associated with the Assassin Brotherhood. Its historical setting predates the traditional medieval Assassins by many centuries.