Frederick was born in 1122. In 1147 he made his first trip to the East, accompanied by his uncle, the German king Conrad III, on the Second Crusade. The expedition proved to be a disaster, but Frederick distinguished himself and won the complete confidence of the king. When Conrad died in February 1152, only Frederick and the prince-bishop of Bamberg were at his deathbed. Both asserted afterwards that Conrad had, in full possession of his mental powers, handed the royal insignia to Frederick and indicated that Frederick succeed him as king. Frederick energetically pursued the crown and at Frankfurt on 4 March 1152 the kingdom's princely electors designated him as the next German king.

Eager to restore the Empire to the position it had occupied under Charlemagne and Otto I the Great, the new king saw clearly that the restoration of order in Germany was a necessary preliminary to the enforcement of the imperial rights in Italy. So, Frederick undertook six expeditions into Italy. In the first, on 18 June 1155, Pope Adrian IV crowned Frederick I Holy Roman Emperor at St Peter's Basilica, Vatican City. Frederick was faced with the reality of disorder among the German states. Italian unity under German rule was more myth than truth. There began to be a generalized social desire to "create greater Germany" by conquering the Slavs to the east.

In 1189 Frederick embarked on the Third Crusade, a massive expedition in conjunction with the French, led by king Philip Augustus, and the English, under Richard the Lionheart. He organized a grand army of 100,000 men and set out on the overland route to the Holy Land. On 10 June 1190, Emperor Frederick drowned in the Saleph river. He had decided to walk his horse through the river instead of crossing the bridge that had been too crowded with troops. The current was too strong for the horse to handle, and his suit armour was too heavy for him to swim in: both were swept away and drowned. Some historians believe he may have had a heart attack that complicated matters. Some of Frederick's men put him in a barrel of vinegar to preserve his body.