The Sack of Thessalonica was in 904 A.D. by the Saracen pirates, one of the worst events and disasters which had befallen the Byzantine Empire in 10 century A.D. There was a Muslim fleet led by the renegade, Leo of Tripoli who had targeted Constantinople the capital of the Byzantine Empire Leo had travelled from Syria to carry out the sacking. However, the Muslims changed from attacking the capital, Constantinople and set their sights on Thessalonica. The Byzantines were taken by surprise and was not able to mobilize and reach their navy in time to stop the pirates. The two commanders had also issued conflicting orders.

After a while and a short siege, the Saracens stormed the walls and had taken Thessalonica on 29th July, having freed 4,000 Muslim prisoners and capturing 60 ships. They had gained a large amount of loot, with 22,000 captives, and young people as well.