The Sassanian Empire, also known as the Sassanid Empire, was a major Persian empire that existed from 224 to 651 CE. It was founded by Ardashir I after defeating the Parthian Empire. The Sassanian Empire is known for its achievements in art, architecture, and science, as well as its role in the development of Zoroastrianism as the state religion. The empire was characterized by a centralized government and a strong military. It expanded its territory to include parts of the modern-day Middle East, including Iran, Iraq, and Armenia. The Sassanian Empire eventually fell to the Arab Muslim conquests, leading to significant cultural and religious changes in the region.