The Sasanian Empire , officially Ērānšahr (Middle Persian: 𐭠𐭩𐭥𐭠𐭭𐭱𐭲𐭥𐭩, lit. 'Empire of the Iranians'), was the last empire of ancient Iran. Named after the House of Sasan, it endured for over four centuries, from 224 to 651, making it the second longest-lived imperial Iranian dynasty after the directly preceding Arsacid dynasty of Parthia. In the seventh century it fell to the Rashidun Caliphate during the early Muslim conquests, which marked the beginning of a monumental societal shift by initiating the Islamization of Iran. Upon succeeding the Parthians in the third century, the Sasanian dynasty re-established the Persian nation as a major power in late antiquity, and also continued to compete extensively with the neighbouring Roman Empire. It was founded by Ardashir I, a ruler who rose to power as Parthia weakened amidst internal strife and the Roman–Persian Wars. After defeating Artabanus IV of Parthia during the Battle of Hormozdgan in 224, Ardashir's dynasty replaced that of the Arsacids and promptly set out to restore the legacy of the Achaemenid Empire by expanding the newly acquired Sasanian dominions. At its greatest territorial extent, the Sasanian Empire encompassed all of modern-day Iran and Iraq and parts of the Arabian Peninsula (particularly Eastern Arabia and South Arabia), as well as the Caucasus, the Levant, and parts of Central Asia and South Asia. One of the high points in Iranian civilization, the Sasanian dynasty's rule was characterized by a complex and centralized government bureaucracy, and also revitalized Zoroastrianism as a legitimizing and unifying ideal. This period saw the construction of many grand monuments, public works, and patronized cultural and educational institutions. The Sasanian Empire's cultural influence extended far beyond the physical territory that it controlled, impacting regions as distant as Western Europe, Eastern Africa, and China and India. It also helped shape European and Asian medieval art. With the Muslim conquest of Persia, the influence of Sasanian art, architecture, music, literature, and philosophy was gradually absorbed into nascent Islamic culture, which, in turn, ensured the spread of Iranian culture, knowledge, and ideas throughout the expanding Muslim world. Source: Wikipedia (en)