According to mythology, the island of Kefalonia was named after the mythical persona of Kefalos who was a mixture of two different mythical people. He was the son of Dion and Diomeda and Mercury, or the son of Pandion and Kreoussa, or Ersi. The goddess Jo loved king Kefalos and, in order to make him hers, she made him doubt the loyalty and devotion of his wife, Prokris. Jo encouraged him to appear before his wife wearing a disguise, and to seduce her with gifts. Prokris gave in to Kefalos and when she realized who he really was, she left, crying desperately. After Prokris wandered around Crete, she returned to Athens where the goddess Diana agreed to help her win back her husband. Unfortunately, while hunting, Kefalos saw the movement of Prokris behind the trees and, mistaking her for prey, he aimed at her and killed her. Desperate from his misfortune, Kefalos left Athens. He met Amphetryon and helped him defeat the Televoes and the Tafious. In return, Amphetryon offered Kefalos this island, which he called "Kefalonia". According to another legend, the island was named after Kefalines of Kefalanes, a nation in western Greece. Many students claim that Kefalines were the Ulysse's people thus his kingdom was on the island of Kefalonia. Those who agree with this option, spell the island's name with two "ls".

Excavations indicate that the island of Kefalonia has been inhabited since at least 10,000 BC and maybe even since 50,000 BC. The existence of Paleolithic civilizations on the island is verified by the findings at Fiskardo, Skala, Agios Georgios, Sami, Mounda, Poros and Argostoli. These findings are related to those from southern Italy and the rest of Greece. Nevertheless, the investigation concerning the dating of the findings has not yet been concluded. Another known fact is of the existence of a significant civilization on the island during the Bronze Era, the Proto-Hellenic Era (3,000-2,000 BC) and the Mid-Hellenic Era (2,000-1,500 BC). The mycenaean tombs which were brought to light during the excavations at Mazarakata, Metaxata, Diakata Kranias, Lakithra, Mavrata and elsewhere, indicate that the island thrived during the mycenaean years, around 1,600 BC, a phenomenon not observed for any other Ionian island. This occurred, among other reasons, because of the enormous corn production on the island, as well as Kefalonia's commercial contacts with Ithaki and the town of Nidri, in Lefkada. According to another tradition, the island of Kefalonia was introduced to the mycenaean civilization by emigrants to the Southern Peloponnese, Western Greece and Attica. This is indicated by similar findings from these areas.

Herodotus is the first historian ever to refer to the island by the name of Kefalinia, while Thucydides called the island "Tetrapoli" (: Four cities), because of the towns of Pali, Sami, Kranea (alias Krani) and Proni, which thrived during the mycenaean years. The most significant of all the cities was Sami, on the northeastern part of the island. Pali was situated on the western peninsula, in the location of Palaiokastro; Krani was situated by the Lagoon of Koutavos where Argostoli stands today; and Proni was situated on the southeastern part of the island. The four cities were not related to each other and had separate coins and regimes. The inhabitants of the islands worshipped the Olympian Gods and performed sacrifices in the temples in order to please the gods. Hesiodus refers to the temple of Ainios Zeus on mount Aino, while the existence of a second temple of Zeus, is also mentioned on the isle south of Kefalonia. Kefalonia participated in the Persian Wars, in the battle of Plataies (479 BC) and in the Peloponnesian War, supporting both Sparta and Athens, as every city supported its political preference. In 218 BC, king Philip from Macedonia attacked the island and attempted to occupy it, but Athens helped Kefalonia defeat him.

In 187 BC, the Romans occupied the island of Kefalonia. Despite the resistance of the locals, the Romans conquered the island and destroyed Sami. During the Roman Rule, the inhabitants of Kefalonia were constantly threatened with raids by pirates and conquerors who took away their fortunes, thus making life on the island impossible. In 50 BC, the island was ruled by Gaius Antonios. In the second christian century, Poplius Aelius Adrianus offered the island as a present to Athens, and the island, the area surrounding Sami in particular, progressed economically.

During the Byzantine Era, the island of Kefalonia was often raided by pirates. The island, along with 64 other provinces and 935 cities, belonged to the Byzantine emperor. In the 10th century AD, Constantinos Porfyrogenitos indicated that the island was part of the "Scheme of Kefalonia", which was established by the Leon VI´, as the remaining seals prove. The Byzantine Era ended in 1085, when Robert Guscard attempted to occupy the island.

In 1084, the adventurer Robert Guiscard attempted to occupy the island of Kefalonia, but he did not succeed, as the locals fought successfully against him. He then retired to the village of Fiskardo where, years later, he died after naming the village after himself. Consequently, the Normand noble Boimond took violent revenge against the locals who dared to resist Guiscard. In 1103 and 1125, the Crusaders attacked the island. Kefalonia was briefly occupied by the Normand Roger B´, in 1147, but the Byzantine emperor Manuel, with the help of the Venetians, defeated Roger B´. Nine years later, Manuel signed a treaty for peace and released the Ionian Islands, including Kefalonia, to the Normands. In 1185, the Sicilian King Gullielmo B´ gave Kefalonia to Admiral Margaritoni, as part of the "Palatian Country of Kefalonia and Zakynthos". Margaritoni's successor was appointed in 1194. He was the pirate Matteo Orsini, who constantly raided the surrounding areas. The Orsini family with the help of a multitude of rogues and murders ruled the island for 150 years, when they were succeeded by the Tokos dynasty, in 1357. Kefalonia was ruled by this dynasty until 1479, when Turks conquered the island.

In 1500, the Venetians and the Spanish, violating the treaty verifying Turkish dominion upon Kefalonia, attacked and conquered the island. Venetian Rule lasted 300 years with the help of local nobles who were granted a series of privileges, while the common people lived in poverty. In 1538, the Turk pirate Hairedin Barbarossa attacked Kefalonia, causing severe damage while capturing 13,000 slaves. In spite of this, hundreds of people from the mainland came to the island, fortifying the Greek presence in the area. During the last years of the Venetian Rule, there were severe disputes between the rich families of the island. The Venetian Rule ended in 1797, when the French occupied the island.

On 28 June 1797, the French occupied the island of Kefalonia. Napoleon made the locals believe that he would liberate the Ionian Islands. The book describing the names and the privileges of the nobles, "Libro d'oro", was burnt in the square of Argostoli, while the people celebrated. The French rule of the Ionian Islands became official with the Treaty of Kamboformio on 17 October 1797. The Ionian Islands became part of the French State on 1 November 1797. The following year, the allied fleet of the Russians, the Turks and the English defeated the French at Aboukir and their fleet disembarked at Argostoli, where a government was appointed, its president being K. Horafas. On 21 March 1800, in Constantinople, the "Ionian State" was founded under the Sultan's supervision. The rich nobles of the island were granted exclusive privileges for ruling, a fact which caused insurrections on all the Ionian Islands, which were violently suppressed by the conquerors. In 1802, by popular demand, Kefalonia's elections took place and new, democratically elected representatives were charged, on 23 December 1803, with the creation of a new Constitution which would later establish the "Democracy of the Ionian Islands". In 1807, the Ionian Islands came under the French rule again, and Field Marshal Berthieux was in command. After several changes, the "Democracy of the Ionian Islands" was maintained and people hoped for a peaceful, normal life. Unfortunately, their hope did not last for long, as the English occupied Zakynthos, on 19 September 1809.

On 19 September 1809, the English occupied Zakynthos and later, in spite of the French's objection, all the Ionian Islands, came under English occupation, which became official with the establishment of the "United States of the Ionian Islands", with the Treaty of Paris. According to this treaty, the Ionian Islands were to be under the command of the English Lord Commissioner. During the English Occupation, Kefalonia obtained significant constructions, such as the bridge of Drapano which joins Argostoli with the Lagoon of Koutavos, a constitution supervised by Charles Philippe de Bossé from Switzerland. The Constitution of 28 December 1817 imposed a series of unpopular measures which made the local's life even more difficult. The people of Kefalonia, along with other inhabitants of the Ionian Islands, resisted the despotic rule of the English by founding secret committees and secretly mounting insurrections.

Although the island of Kefalonia remained under the English Occupation, the locals participated actively in the Greek Revolution against Turkish Rule. Some of the fighters from Kefalonia were Constantinos and Andreas Metaxas, Gerasimos and Dionissios Fokas, Demetrios Hoidas, Gerasimos Orfanos and Loukas Valsamakis. The most significant event in which Kefalonia participated was the battle of Lalas, in Helia. There, with the help of the Peloponnesian army, Andreas and Constantinos Metaxas defeated the Turks who invaded the village on 24 June 1821. At that time, the Ionian Commissioner was Charles Napier, a democrat who supervised significant constructions in Kefalonia, one of them being the building "Markato" at Lixouri, which initially housed the island's Court. On 14 September 1848, due to popular demand, Ionian Commissioner Seaton granted the people significant privileges. The next Commissioner, George Eward, wished to change the Constitution, yet he was prevented by the Conservatives. A new series of insurrections forced Queen Victoria to proclaim elections in 1850, after which the first Parliament was established. The Parliament's duration was short, as it dissolved after the union of the Ionian Islands with the rest of Greece. The crisis of the English policy regarding Greece and the people's insurrections forced England to secede from the dominion of the Ionian Islands and on 23 September 1863, the Parliament voted in favor of their union with the rest of Greece. On 21 May 1864, Thrasivoulos Zaimis officially received the Ionian Islands from Henry Storcks.

During World War II, Kefalonia was occupied by the Italians in 1941 and the Italian army settled on the island. The people of Kefalonia were actively involved in the Greek Resistance and fought for the country's liberation. In September 1943, the German-Italian combat in Kefalonia, caused by the Italians' refusal to withdraw from the island's rule in favour of the Germans, cost 9,500 Italian soldiers their lives. Ten years later, in 1953, the earthquake which rocked the Ionian Islands, caused severe damage to Kefalonia. The majority of the houses in Argostoli collapsed and the locals fought hard to restore their life.

Georgios Bonanos was born in Vouni, Kefalonia in 1863. He studied sculpture at the School of Fine Arts in Athens. His teachers were Lazaros Fytalis, Leonidas Drosis, and Dimitris Filippotis. He completed his studies in Rome. His work is characterized by vigour, skill, and dynamism. He died in Athens in 1940. Among his most significant works are "Greek Slave", which received an award at the International Fair of Paris in 1889 and "Huntress", which also received an award in 1900. Other works of his include "Hours", "Dead Woman" in the 1st cemetery of Athens, the monument of Iakovati in Lixouri, and the Toole monument in the English cemetery of Argostoli. He also made busts such as that of Panagiotis Vallianos in the National Library of Athens, Miaoulis in Syros, Odysseas Androutsos in Gravia and others.

Marinos Korgialenios, the island's benefactor, was born in Argostoli in 1830. In his youth he worked in the trading houses of Smyrna and Odessa. He was involved in trade and founded his own enterprises in London and Marseille, in 1859 and 1863 respectively. In 1875, he established a bank agency in London, where he died in 1911. After his death, he bequeathed a large fortune to his birthplace, which, among other things, helped build the "Korgialenio Museum" in Argostoli.

Andreas Metaxas, was born in Kefalonia in 1790. During the Greek War of Independence he fought for the overthrow of the Turkish yoke. With a force of about 300 soldiers and troops from the Peloponnese, he, with his cousin Konstantinos Metaxas as co-captain, took over the village Lala of Ilia on 24 June 1821. Later, he was appointed a member of the legislative body of the 2nd National Assembly and was sent to Verona to ask for assistance from the Great Powers on the Greek issue. He also helped Kapodistrias in the fulfillment of his difficult task, when the latter came to Greece. In the years of the Bavarians, he became prefect of Lakonia and later was exiled to Syros and Marseille. In 1835, in the years of regency, he was appointed ambassador of Greece in Madrid and Lisbon. He was elected Minister of War in Mavrokordatos's administration and later became ambassador to Constantinople. After the revolution of 3 September 1843, he formed a government for the voting of a constitution. He died in 1870.

Andreas Laskaratos was born in Lixouri in 1811. He lived on the island in the period of the great machinations when British rule was showing its authoritarian face. He studied law in the Ionian Academy, Paris, and Pisa. He met and was influenced by Andreas Kalvos and Dionysios Solomos. In 1856, he wrote Mysteries of Kefalonia in which he satirized the church and the radicals. He was excommunicated as a result. He wrote in the simple, unrefined language of the people and his works were very popular despite the persecutions he suffered. He spent some time self-exiled in London and then returned home. He published the Lyxnos magazine and suffered new persecutions for his criticisms. He died in 1901 in Lixouri. Other works of his are A Reply to the Excommunication (1856), Pieces in Verse (1872), and Ecce homo (1886).

The composer and musician Dionysios Lavragas was born in Argostoli in 1864. He studied violin, piano, organ, theory of music, composition, and conducting in Naples and Paris. He began his career as conductor of melodrama in Italy and France. In 1894, he was appointed director of the Music Society of Athens and at the same time taught music in the Arsakeio School. In 1897, he founded the musical department of the G. Fexis Musical Publishing House. In 1898, he started giving performances of professional melodrama. Between 1901 and 1905, he taught in the Greek Conservatory. He worked as a journalist for the Eleftheron Vima and Ethnos newspapers. He was awarded the Medal of Letters and Arts for his contribution to the Greek melodrama and modern Greek music. He died in Argostoli in 1941. His compositions include "The First Greek Suit" (1903), the symphonic piece "Fuga", the melodramas "Dido" and "Life is a Dream", the opera "Fakanapa's Torments", the dramas "The Redeemer" and "The Black Butterfly", and the operettas "White Hair" and "Double Fire". Of particular note is his religious work "Misa Solemnis". He also wrote books about the theory of music like the Manual of Harmony, Theory of Music and The Handbook of Musical Art.