A succession of empires which ruled the Iranian plateau. In 1935 the name Persia was changed simply to Iran.
The Persians controlled a vast amount of territory, including most of the Middle East, Turkey and a portion of Northern Africa--primarily under Cyrus the Great. Accordingly, the Persian empire was one of the first great empires of the world. They were unstoppable and greatly feared until Alexander the Great conquered them and far more.
After Alexander the Great died, Parthians (based in modern-day Iran) tried unsuccessfully to reestablish the Persian empire. But their past greatness was not achieved again. They could not withstand the Roman army, which conquered it in A.D. 226.
Afterwards, a Persian noble named Ardashir seized power by killing the Parthian king, and established the Sassanid empire along with the official state religion of Zoroastrianism, a polytheistic religion that had a creator (Ahuramazda) and a sun-god (Mithra). This religion was essentially limited to Persians. It made no attempt to convert others and it tolerated other religions in the region like Judaism. Its greatest king was Shapure II (A.D. 309-379), who beat back the weakening Romans and also extended Persian power towards China. This empire remained in control of Persia until Muslims took control of the region in A.D. 651.