Ardashir I was the founder of the Sasanian Empire, which emerged in Persia around 224 CE. He rose to power after defeating the last ruler of the Parthian Empire, establishing a new dynasty that would last for over four centuries. Ardashir is known for his military prowess and administrative reforms, which helped unify and strengthen the empire. Under Ardashir's rule, the Sasanian Empire expanded significantly, promoting Zoroastrianism as the state religion. He is often credited with revitalizing Persian culture and governance, setting the stage for a flourishing civilization that would influence future empires, including the Byzantine Empire and Islamic Caliphates.