The Duchy of Athens was one of the Crusader States set up in Greece after the conquest of the Byzantine Empire during the Fourth Crusade.
The first duke of Athens (as well as of Thebes, at first) was Otto de la Roche , a minor Burgundian knight of the Fourth Crusade. Although he was known as the "Duke of Athens" from the foundation of the duchy in 1205, the title did not become official until 1280.
Athens was originally a vassal state of the Kingdom of Thessalonica, but after Thessalonica was captured in 1224 by Theodore, the Byzantine Despot of Epirus, the duchy became a vassal of the Principality of Achaea. The Duchy occupied the Attic peninsula and extended partially into Macedonia, sharing an undefined border with Thessalonica and then Epirus. It did not hold the islands of the Aegean Sea, which were Venetian territories. The buildings of the Acropolis in Athens served as the palace for the dukes.
The de la Roche family held the duchy until 1308 when Walter V of Brienne became duke. Walter hired the Catalan Company, a group of mercenaries founded by Roger de Flor, to fight against the Byzantine successor states of Epirus and Nicaea, but when he tried to outsmart them in 1311 they overthrew Walter and took over the Duchy, making Catalan the official language and replacing the French and Byzantine-derived laws of the Principality of Achaea with the laws of Catalonia. Walter remained in possesion of Argos and Nauplia where he was titled Duke.
In 1318/1319 the Catalans conquered Siderocastron and the South of Thesalia and created the Duchy of Neopatria , united to Athens. Part of Thesalia was conquered by Serbs in 1337.
In 1379 the Navarrese Company at service of the Emperor Jacques de Baux conquered Thebes and part of Neopatria . Meanwhile, the Catalans kept another part of Neopatria and Attica.
After 1381 the Duchy was ruled by the Catalan kings of Aragon and Sicily until 1388 when the Acciajuoli family of Florence bought Athens. Neopatria was occupied in 1390.
From 1395 to 1402 the Venetians briefly controlled the Duchy. In 1444 Athens became a tributary of Constantine Palaeologus, the despot of Morea and heir to the Byzantine throne. In 1456, after the Fall of Constantinople to the Ottoman Empire, Sultan Mehmed II conquered the remnants of the Duchy.
Dukes of Athens
- Mateu de Montcada
- Roger de Llúria
- Mateu de Peralta
- Luis Frederic of Aragon
- Viscount of Rocabertí
- Bernat de Cordella