Alexander was born in Baggio in Italy. He became a priest and in 1057 was appointed as Bishop of Lucca. He undertook reforms and campaigned against morality and corruption in the Catholic Church. However, he was totally opposed to one suggested reform, the marriage of priests.

In 1061 Alexander was elected pope. However, the Germans disagreed with Alexander's election and appointed their own pope, Honorius. In 1066 Alexander took the controversial decision of giving William of Normandy permission to invade England.

Alexander II died in 1073.