The island of Kephalonia, is the largest of the Ionian Islands in western Greece, with an area of 350 sq. miles. It is also the larger of the two islands forming the Kephalonia and Ithaka Prefecture, and contains eight of the prefecture's nine municipalities or communities. (Ithaca is on a separate island.)
The island is named after the mythological figure Cephalus (Ciphalis), although some hold its name literally means "island with a head", referring to the island's shape; the name "Ciphalis" is derived from the Greek word for "head".

The capital of the Kefalonia prefecture is Argostoli. The island's population is nearly 45,000; it previously was home to the fastest growing population in Greece, with a growth rate of 35% to 40% during the 1990s. It was officially 36,404 at the census of 2001. The size of the island is ca. 800 km2 (300 mi2), and the present population density is 55 people per km2 (140/mi2), with Argostoli home to one-third of the island's habitants. Lixouri is the second major settlement, and the two towns together account for almost two-thirds of the prefecture's population.
Kefalonia is located in the heart of an earthquake zone, and dozens of minor or unrecorded tremors occur each year. In 1953, a massive earthquake almost destroyed settlement on the island, leaving only Fiscardo in the north untouched.
Most of the Kefalonia population have surnames ending in "-atos". Almost every community in Kefalonia has a name ending in "-ata", such as Valsamata, Frangata, Lourdata, Favata, Delaportata, and others.
In the ancient period, before it was named Kefalonia, the island was known to have a population of only 100 to 300; at the ancient founding of Kefalonia, the population trebled to around 500 - 1,000 people. The population grew steadily, until it reached 10,000 in the mid-20th century, with the total topping 20,000 by the 1970's.

There are five harbours and ports in the prefecture: four main harbours on the island, Same or Sami, and a major port with links to Patras and Ithaca. Poros, in the south, has ferry routes to Kylini; Argostoli, in the west, is the largest port, for local boats and ferries to Zante and regularly to Lixouri; Fiscardo, in the north, has links to Lefkas and Ithaca. There is room for about 100 small boats in Argostoli, where the port stretches 1 kilometre around the bay, while Lexouri is situated 4 km across the bay from Argostoli, on the Lixouri peninsula. There is a road connection to the rest of the island, but driving from Lexouri to Argostoli involves a 30 km detour.
Kefalonia has one airport, Kefalonia Island International Airport, with a runway around 2.4 km. in length, located about 10 km south of Argostoli. Almost every scheduled flight is an Olympic route, flying mainly to and from Athens, although there is an Ionian Island

Monasteries

Across the broader island two large monasteries are to be found: the first is that of Haghia Panagia, in Markopoulo to the southeast, and the other lies on the road between Argostoli and Michata, on a small plain surrounded by mountains. This second has an avenue of about 200 trees lined from NW to SE with a circle in the middle, and is the monastery of Agios Gerasimos, patron saint of the island whose relics is on show for veneration at the old church of the monastery

Museums

Korgialeneios Museum (under the Korgialeneios Library) in Argostoli
Kosmetatos Foundation in Argostoli
Archaeological Museum in Argostoli
Iakovatios-Library in Lixouri
Museum in Fiscardo

A large number of tourists visit Kephalonia during the peak season but, as one of the largest islands in Greece, it is well-equipped to handle visitors. Most tourists stay in or around Lassi, a serene resort a few kilometres from Argostoli and in the villages Skala and Katelios in the Municipality of Elios-Pronni. Their numbers have increased since the best-seller, Captain Corelli's Mandolin, was made a film (2001) shot on the island itself. Many people from all over Greece and the world visit Kefalonia. Many tourists come from Italy mostly because of its close location.
The island is covered by dense vegetation and offers a great range of natural beauty, including beaches—many of them inaccessible from land—and spectacular caves. Mirtos, the most famous of these beaches, is a major tourist attraction, and has been ranked fifth worldwide for its beauty. Fishing is very common throughout the waters within and around the island, and the harbours of Argostoli and Lixouri are the main fishing centres. Overfishing can be a problem in Kephalonia, and in the Ionian area generally.