Which is the oldest religion

From a Jain perspective, Jainism is considered an eternal dharma (absolutely timeless), not something that began at a specific point in history. Jains believe that the Tirthankaras teach an eternal path to liberation that has always existed, though individual Jain communities have a long historical record.

In common historical terms, many ancient traditions claim great antiquity. Hinduism, Judaism, Buddhism, and Zoroastrianism are among the religions often described as very old. So, while Jainism itself describes its path as timeless, there isn’t a single agreed-upon “oldest religion” label that excludes other ancient traditions.