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 Sassanids are known for their advancements in art, architecture, and science, as well as their promotion of Zoroastrianism as the state religion. The empire reached its height under rulers like Khosrow I, expanding its territory across the Middle East and into parts of Europe and Asia. The Sassanids frequently clashed with the Roman Empire, influencing the cultural and political landscape of the region until their fall to the Arab conquests.