<P> In the Western world, Persia (or one of its cognates) was historically the common name for Iran . On the Nowruz of 1935, Reza Shah Pahlavi asked foreign delegates to use the term Iran, the endonym of the country, in formal correspondence . Since then, in the Western World, the use of the word "Iran" has become more common . This also changed the usage of the terms for Iranian nationality, and the common adjective for citizens of Iran changed from "Persian" to "Iranian". In 1959, the government of Mohammad Reza Shah Pahlavi, Reza Shah Pahlavi's son, announced that both "Persia" and "Iran" could officially be used interchangeably . However the issue is still debated today . </P> <P> The Modern Persian word Īrān (ایران) derives immediately from Middle Persian Ērān (Pahlavi spelling: ʼyrʼn), first attested in an inscription that accompanies the investiture relief of the first Sassanid king Ardashir I at Naqsh - e Rustam . In this inscription, the king's Middle Persian appellation is ardašīr šāhān šāh ērān while in the Parthian language inscription that accompanies the Middle Persian one the king is titled ardašīr šāhān šāh aryān (Pahlavi:...ʼryʼn) both meaning king of kings of Iranians . </P>

When did the name of persia change to iran