Which of the following is the largest animal rights organization in the world?

The largest animal rights organization in the world is People for the Ethical Treatment of Animals (PETA). Founded in 1980, PETA has gained significant international recognition and influence in advocating for animal rights. Their campaigns focus on promoting veganism, opposing animal testing, and highlighting the ethical treatment of animals in various industries. PETA's expansive outreach includes educational programs, celebrity endorsements, and high-profile demonstrations, which contribute to its prominence as a leading organization in the animal rights movement.

While other organizations such as Humane Society International and World Animal Protection are also significant players in animal welfare and protection, they often focus on broader animal welfare issues rather than solely on the rights of animals. The Animal Legal Defense Fund is focused specifically on legal matters relating to animal rights, making it a critical organization as well, but it does not have the same global reach or recognition as PETA. Thus, the status of PETA as the largest animal rights organization is rooted in its widespread influence and advocacy efforts across a range of issues related to animal rights.