The goddess represented by the statue in Assassin's Creed Origins' opening cinematic is Sekhmet.
Sekhmet is an ancient Egyptian goddess commonly depicted with a lioness head and associated with war, protection, and destructive power. Her image appears in the game's opening presentation, establishing the Egyptian setting and its religious imagery before Bayek's story begins.
Assassin's Creed Origins uses real Egyptian names, places, gods, and historical figures within a fictional narrative. The game is set during the Ptolemaic period, when Greek and Egyptian traditions existed together, and its world includes temples and monuments inspired by surviving archaeology.
Isis, Bastet, and Hathor are also genuine Egyptian goddesses, which makes them plausible alternatives. Bastet is especially easy to confuse with Sekhmet because both can be represented as feline deities, but the opening statue is identified with Sekhmet.