As of 2016, the country formerly known as Persia is the Islamic Republic of Iran. Iran is sometimes referred to as Persia, though it is not its official name.
Short History of Persia
The Persian Empire is any of a series of imperial dynasties centered in Persia currently known as Iran, first established by Cyrus the Great in 550 BC.Persian dynastic history was interrupted by the Islamic conquest in 7th century and later by the Mongol invasion. Main religion of ancient Persia was Zoroastrianism, but after the 7th century this was replaced by Islam. And Since 1979 Persia has been known as "Islamic republic of Iran"
See the Persian empire at its Zenith under Achaemenid Empire