Who led the Russian Revolution?

Vladimir Lenin and his Bolshevik Party.

Actually there where two revolutions. In the first one that took place in February (March, New Style)the workers, peasants and soldiers rioted in the streets against the Tsar. When the army and police refused to obey his orders to quell the riots, the Tsar abdicated and his government simply collapsed. A Provisional Government was formed to step in and keep peace until a new constitutional assembly could be seated. The Duma did not overthrow the tsar. So Nicholas the second was the last tsar of Russia. Later in October (November, New Style), there was another revolution where the Bolshevik Party and the Soviet councils replaced the Provisional Government. After this there was civil war for about three years which left the Bolsheviks in charge of the the USSR.