Zoroaster, also known as Zarathustra, was a religious reformer and the spiritual founder of Zoroastrianism. He founded the first documented monotheistic religion in the world and also had an impact on Plato, Pythagoras, and the Abrahamic religions, including Judaism, Christianity, and Islam. Zoroastrians believe that he was a prophet who transmitted God's messages and founded a religious movement that challenged the existing traditions of ancient Iranian religion, while in the minority Ahmadiyya branch of Islam and in the Baháʼí Faith, he is also considered a prophet. He was a native speaker of Avestan and lived in the eastern part of the Iranian plateau, but his exact birthplace is uncertain.