The pyramids are aligned with the stars of Orion’s belt, which the ancient Egyptians associated with Osiris, the god of the afterlife. The three pyramids of Giza, Khufu, Khafre, and Menkaure, correspond to the three stars of Orion’s belt, Alnitak, Alnilam, and Mintaka, respectively.
The sizes and positions of the pyramids match the relative brightness and locations of the stars.
But there's also a theory that claims that the south shaft of the Great Pyramid of Khufu was designed to point to the culmination point of Orion’s belt, which occurred around 10,450 BC, when the stars reached their highest altitude in the sky...