Zarathustra : The Golden Star deals with the life and doctrine of Ashoo Zarathustra, the ancient Iranian Prophet - and the destiny of Zarathustrianism (Mazdaism) up to the end of the Sassanid dynasty (224 - 651 AD). First we go through the description of the historical background of the various existing religions before Zarathustra, and then the amazing birth of Zarathustra, his social status, his upbringing and his struggle to promote his faith. We follow him to Bactria meeting King Vishtaspa, the supporter of Zarathustra and explore the reasons for two wars between Iran and Turan. We study the Zarathustrianism, Zurvanism, Manichaeism and Mazdakism up to the Arab conquest of Iran (637 - 651 AD). For a better understanding and clarity of the essence of this study, Zarathustrianism is divided into three different outlines, namely: 1) The Pre-Zarathustrianism, which considers all conventional faiths before Zarathustra's emergence 2) The Canonical-Zarathustrianism, which details all major events from Zarathustra's birth to death, 3) The Post-Zarathustrianism [or PZ in short], which recounts all the occurrences after the death of Zarathustra.