The Middle Ages were also the time of the Crusades. They were originally intended to reclaim the Holy Land from Muslim hands, although political pressures sometimes took them in surprising directions.

The First Crusade was the only de facto successful expedition. Launched by Pope Urban in 1096, it resulted in the capture of Jerusalem and the creation of the County of Edessa (1098), the Principality of Antioch (1098), the County of Tripoli (1104), and the Kingdom of Jerusalem (1099). However, less than a century later, Jerusalem was recaptured by Saladin's army in October 1187.

The 4th expedition, contrary to its original plans to help the Latin states in the Middle East, was bribed by a Venetian doge and used to capture Constantinople.

The 5th set out for Egypt, but was driven out after initial military successes.

The last two crusades ended in defeat and the withdrawal of troops. In total there were seven crusades. The last one took place in 1270. Of the four crusader states formed during the First Crusade, the Kingdom of Jerusalem lasted the longest, until 1291.