Ithaca or Ithaka (in Greek, Ιθάκη, Ithaki; see also List of traditional Greek place names) is an island in the Ionian Sea, in Greece, with an area of 96 km² (37 sq. miles) and three thousand inhabitants. It is an independent municipality of the prefecture of Kefalonia, and lies off the northeast coast of Kefalonia. The municipality of Ithaca includes some smaller islands as well. The capital, Vathy, has one of the world's largest natural harbours.

The origin of the first people to inhabit the island, which was during the last years of the Neolithic Period (4000-3000 BC), is unknown. The traces of buildings, walls and a road from this time period prove that life existed and continued to do so during the Early Hellenic era (3000-2000 BC). In the pre-Mycenaean years (2000-1500 BC), some of the population migrated to the southern part of the island. The buildings and walls that were excavated showed the lifestyle of this period had remained primitive.

During the Mycenaean period (1500-1100 BC), Ithaca rose to the highest level of its ancient history. The island became the capital of the Cephalonian states, which included the surrounding islands, and the opposite lands, and was referred to as one of the most powerful states of that time. The Ithacans were characterized as great navigators and explorers with daring expeditions reaching further than the Mediterranean Sea.

The epic poems of Homer, the Iliad and the Odyssey, may shed some light on Bronze-Age Ithaca. Those poems are generally thought to have been composed sometime within the 8th to 6th centuries BC, but are based on older mythological and poetic traditions; their depiction of the hero Odysseus, and his rule over Ithaca and the surrounding islands and mainland, may preserve some memories of the political geography of the time.

After the end of the Mycenaean period, Ithaca's influence diminished, and it came under the jurisdiction of the nearest large island.

During the ancient Hellenic prime (800-180 BC) the Corinthians neglected the small and barren island. Independent organized life continued in the northern and southern part of the island. In the southern part, in the area of Aetos, the town Alalcomenae was founded. From this period, many objects were found during excavations, which were of important historical value. Among these objects were the coins imprinted with the name Ithaca and the image of Ulysses and that it was self-governed.

According to the different periods, the conquerors and the circumstances, the population of the island kept changing. Although there is not definite numerical information until the Venetian period, it is believed that from the Mycenaean to the Byzantine period the number of inhabitants was several thousand, who lived mainly at the northern part of the island. During the Middle Ages, the population decreased due to the continuous invasions of the pirates, which forced the people to live on the mountains establishing settlements.

In 1479, Turkish forces landed on the islands setting villages on fire, plundering, killing people and taking captives. Many of the people fled from the island out of fear of the Turkish occupiers. Those that remained were hiding up in the mountains to avoid the pirates who controlled the channel between Cephallonia and Ithaca and the bays of the island. In the following five years, the Turks, Toques and Venetians placed claims on the islands diplomatically. The possession of the islands were finally given the Turkish Empire (1484-1499 A.D.).During this time, the Venetians had strengthened into major power with an organized fleet. The Ionian Islands were part of their pursuits, and in 1499, a war between the Venetians and the Turks started. The allied fleets of the Venetians and the Spanish besieged Ithaca, and the other islands. The fleets prevailed, and from 1500 A.D., the Venetians controlled the islands. According to a treaty of 1503, Ithaca, Cephallonia and Zante belonged to the Venetians, and Lefkada to the Turks.

A few years after the French revolution, the Ionian area came under the rule of the French Democrats (1797-1798 A.D.), and the island became the honorary capital of Cephallonia, Lefkada, and part of the Greek mainland, which formed the Ithacan country.

The population welcomed the French, who took care in the control of the administrative and judicial systems, but later the heavy taxation they demanded, caused a feeling of indignation among the people. During this short historical period, the new ideas of system and social structure greatly influenced the inhabitants of the island. At the end of 1798, the French were succeeded by Russia and Turkey (1798-1807 A.D.), which were allies at that time. Corfu became the capital of the Ionian States, and the form of government was democratic with a fourteen-member senate in which Ithaca had one representative.

The Ithacan fleet flourished when it was allowed to carry cargo up to the ports of the Black Sea. In 1807, according to an agreement with Turkey the Ionian Islands once again came under the French rule (1807-1809 A.D.). The French quickly began preparing to face the English fleet, which had become very powerful, by building a fort in Vathy.

It is worth pointing out of the role, which it played during the struggle of the Greeks against the Turks. Prominent citizens of Ithaki participated in the secret "Filiki Etairia" which was instrumental in organizing the Greek Revolution of 1821, and Greek fighters found refuge there. In addition, the participation of Ithacans during the siege of Messologi and the naval battles with Turkish ships at the Black Sea and Danube were significant.

The island has been inhabited since the 2nd millennium BC. It was the capital of Cephalonia during the Mycenaean period. The Romans occupied the island in the 2nd century BC, and later it became part of the Byzantine Empire. The Normans ruled Ithaca in the 12th and 13th century, and after a short Turkish rule it fell into Venetian hands.

Ithaca was then occupied by France under the 1797 Treaty of Campo Formio. It was liberated by a joint Russo-Turkish force in 1798, before becoming part of the Septinsular Republic. It became a French possession again in 1807, until it was liberated by the United Kingdom in 1809. Under the 1815 Treaty of Paris, Ithaca became a state of the United States of the Ionian Islands, an amical protectorate of the United Kingdom. Under the 1864 Treaty of London, Ithaca, along with the islands, were ceded to Greece as a mark of cordiality with Greece's new king, the Anglophile George I.

Much of the island's architecture was destroyed in an earthquake in 1953.

In the 1970s, Kalamos split from the province and became part of the prefecture of Lefkada, and the province of Ithaca became a non-provincial municipality.

There is also a strait situated in the western part of the island called the Strait of Ithaca.

The capes in the island include Exogi, the westernmost but not in land, Melissa to the north, Mavronos and Agios Ilias to the east, Schinous, Sarakiniko and Agios Ioannis, the easternmost to the east and Agiou Andreou, the southernmost in the south. Bays include Afales Bay to the northwest, Frikes and Kioni Bays to the northeast and Ormos Gulf and Sarakiniko Bay to the southeast. The tallest mountain is Nirito (806 m), the second tallest is Merovigli (669 m).