The Principality of Achaea or Principality of Morea was one of the vassal states of the Latin Empire, which replaced the Byzantine Empire after the capture of Constantinople during the Fourth Crusade. It became a vassal of the Kingdom of Thessalonica, along with the Duchy of Athens, until Thessalonica was captured by Theodore, the despot of Epirus, in 1224. After this, Achaea became for a while the dominant power in Greece.
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 as part of the process known as Frankokratia, encompassing the regions of Attica and Boeotia, and surviving until its conquest by the Ottoman Empire in the 15th century.
William of Villehardouin was the fourth prince of Achaea in Frankish Greece, from 1246 to 1278. The younger son of Prince Geoffrey I, he held the Barony of Kalamata in fief during the reign of his elder brother Geoffrey II. William ruled Achaea as regent for his brother during Geoffrey's military campaigns against the Greeks of Nicaea, who were the principal enemies of his overlord, the Latin Emperor of Constantinople Baldwin II. William succeeded his childless brother in the summer of 1246. Conflicts between Nicaea and Epirus enabled him to complete the conquest of the Morea in about three years. He captured Monemvasia and built three new fortresses, forcing two previously autonomous tribes, the Tzakones and Melingoi, into submission. He participated in the unsuccessful Egyptian crusade of Louis IX of France, who rewarded him with the right to issue currency in the style of French royal coins.
Walter V of Brienne was Duke of Athens from 1308 until his death. Being the only son of Hugh of Brienne and Isabella de la Roche, Walter was the heir to large estates in France, the Kingdom of Naples, and the Peloponnese. He was held in custody in the Sicilian castle of Augusta between 1287 and 1296 or 1297 to secure the payment of his father's ransom to the Aragonese admiral Roger of Lauria. When his father died fighting against Lauria in 1296, Walter inherited the County of Brienne in France, and the counties of Lecce and Conversano in southern Italy. He was released, but he was captured during a Neapolitan invasion of Sicily in 1299. His second captivity lasted until the Treaty of Caltabellotta in 1302.
During the late Middle Ages, the two cities of Argos and Nauplia formed a lordship within the Frankish-ruled Morea in southern Greece.
Isabella of Villehardouin was reigning Princess of Achaea from 1289 to 1307. She was the elder daughter of Prince William II of Achaea and of his third wife, Anna Komnene Doukaina, the second daughter of Michael II Komnenos Doukas, the despot of Epiros.
Guy I de la Roche (1205–1263) was the Duke of Athens, the son and successor of the first duke Othon. After the conquest of Thebes, Othon gave half the city in lordship to Guy.
John I de la Roche succeeded his father, Guy I, as Duke of Athens in 1263. He was cultured and chivalrous, spoke fluent Greek, and read Herodotus.
Guy II de la Roche, also known as Guyot or Guidotto, was the Duke of Athens from 1287, the last duke of his family. He succeeded as a minor on the death of his father, William I, at a time when the duchy of Athens had exceeded the Principality of Achaea in wealth, power, and importance.
Nicholas III of Saint-Omer was one of the most powerful and influential lords of Frankish Greece. He was hereditary Marshal of the Principality of Achaea, lord of one third of Akova and of one half of Thebes. He also served on three occasions as bailli of the Principality of Achaea.
Nicholas II of Saint Omer was the lord of half of Thebes in Frankish Greece from 1258 to his death in 1294. From his two marriages he became one of the richest and most powerful barons of his time, building a splendid castle at Thebes as well as the Old Navarino castle. He also served as bailli of the Principality of Achaea on behalf of the Angevins of Naples between 1287 and 1289.
Bela of Saint Omer was a French knight, descended from a Fauquembergues family who were castellans of the eponymous castle of Saint-Omer.
Otho of Saint Omer was the lord of half of Thebes in Frankish Greece from 1294 to ca. 1299.
John of Saint Omer was baron of a third of Akova and marshal of the Principality of Achaea.
Richard Orsini was the count palatine of Cephalonia and Zakynthos from before 1260 to his death in 1303/4, and also Count of Gravina in 1284–91. He also served on behalf of the Angevin Kingdom of Naples as captain-general of Corfu in 1286–90 and as the bailli in the Principality of Achaea from 1297 to 1300. He assisted the Despot of Epirus in battle against the Byzantine Empire, and secured the marriage of his son, John I, to the Epirote ruler's daughter, which would lead in 1318 to the Orsini takeover of Epirus.
Geoffrey of Briel, in older literature Geoffrey of Bruyères, was a French knight and the third lord of the Barony of Karytaina in the Principality of Achaea, in Frankish Greece. He led a colourful and turbulent life, narrated in detail in the Chronicle of the Morea. Accounted the finest knight in the Principality, he fought in the wars against the Byzantine Greeks, was captured in the Battle of Pelagonia in 1259, and was sent back to Achaea bearing the Byzantine terms in 1261. Geoffrey was twice deprived of his barony, once for rebelling against his uncle, the Prince of Achaea William II of Villehardouin, and then for abandoning the Principality without leave in order to spend time with a mistress, the wife of one of his feudatories, in Italy. He was pardoned both times, but henceforth held his title as a gift of the Prince. He died childless in 1275, and the Barony of Karytaina was split up.
The Barony of Veligosti or Veligosti–Damala was a medieval Frankish fiefdom of the Principality of Achaea, originally centred on Veligosti in southern Arcadia, but also came to include the area of Damala in the Argolid when it came under a cadet branch of the de la Roche family in the 1250s. After Veligosti was lost to the Byzantines towards 1300, the name was retained even though the barony was reduced to Damala.
The First Parliament of Ravennika was convened in May 1209 by Latin Emperor Henry of Flanders in the town of Ravennika in Central Greece in an attempt to resolve the rebellion of the Lombard barons of the Kingdom of Thessalonica.
The Second Parliament of Ravennika was convened in May 1210 by Latin Emperor Henry of Flanders in the town of Ravennika in Central Greece in order to resolve the differences between the princes of Frankish Greece and the Roman Catholic clergy of their domains.
Helena Angelina Komnene was a daughter of the Greek sebastokrator John I Doukas, ruler of Thessaly in ca. 1268–1289, and a Greek princess of Aromanian origin, known only by her monastic name, Hypomone.
