In the mountains of South Korea, a young girl named Mija has spent a decade living a peaceful, pastoral life with her constant companion, Okja, a massive, genetically modified super pig. Okja is one of many such creatures designed by the powerful and ambitious Mirando Corporation, which claims to be addressing world hunger with these new animals. CEO Lucy Mirando has orchestrated a global contest, sending these super pigs to farmers around the world to be raised in natural habitat for a decade before being assessed. However, unbeknownst to Mija, the competition is merely a public relations facade to introduce and market this new product to the masses.

As the contest concludes, Mirando Corporation's officials, led by zoologist and TV personality Dr. Johnny Wilcox, arrive in the idyllic mountainside to take Okja to New York for the final evaluation and a highly publicized event. Determined to prevent her beloved friend from becoming part of the corporate machine, Mija embarks on a daring rescue operation. She must navigate unfamiliar territories, facing the realities of genetically modified food production while confronting the might of Mirando's intricate and influential PR strategy. On her journey, Mija encounters a diverse cast of characters, including animal rights activists led by the well-intentioned but often inept Jay, all while grappling with complex questions about consumerism, ethics, and the bonds of friendship.