Khomeini was born Ruhollah Hendi in 1900 and changed his name to Khomeini in 1930. He was named an ayatollah in the 1950s. In 1964 he was exiled from Iran for his constant criticisms of the government. He fled to Iraq, where he stayed until being forced to leave in 1978, after which he went to France. He returned to Iran in 1979, after helping foment a revolution, became leader and figurehead of the new government, a religious dictatorship which purported to be an Islamic republic. He ruled Iran until his death in 1989.
Khomeini's earlier hostility to the government of Iran owed a lot to the perceived foreign control of Iran, notably by the British and later, the United States. Upon assuming power, Khomeini sought to end foreign and especially Western influence in Iran.
Khomeini supporters called him the 'imam'. In the west he is often referred to as simply 'the ayatollah'.