Skiathos is a small Greek island situated in the northwest Aegean Sea, serving as the westernmost landmass of the Northern Sporades archipelago. Located east of the Pelion peninsula in Magnesia and west of Skopelos, it functions as the primary entry point for the region due to its sole airport and status as the first port of call for most ferries. The island features a north-south axis, measuring approximately 12 kilometres long and 6 kilometres wide, with an indented coastline comprising inlets, capes, and peninsulas that define its geographical character.

The island played a minor role in the Persian Wars before becoming part of the Delian League, though its original city was destroyed by Philip V of Macedon in 200 BC. In 1207, the Ghisi brothers captured Skiathos and constructed the Bourtzi fortress, but pirates forced inhabitants to relocate the capital to Kastro in the mid-14th century. The island passed through Byzantine and Venetian control before being conquered by Ottoman admiral Hayreddin Barbarossa in 1538, later serving as a hideout for Greek rebels during the War of Independence.

The main town, Skiathos, lies in the eastern part of the island, while the rugged north coast contrasts with gentler slopes in the southeast and southwest where most settlements are located. Notable landmarks include the medieval Kastro ruins, the Evangelistria Monastery where the first Greek flag was hoisted in 1807, and the Alexandros Papadiamantis House Museum. The island also features the Bourtzi Peninsula and numerous beaches, with wooded landscapes dominated by Aleppo pine and a stone pine forest at Koukounaries.

Skiathos is the most tourist-intensive island in the Sporades, attracting visitors with its beautiful scenery, quaint tavernas, and lush green terrain suitable for hiking. It gained international fame as a filming location for the 2008 film Mamma Mia! alongside its neighbour Skopelos. The island offers good accommodation and public transport, with popular sites including Koukounaries Beach, Lalaria, and Banana Beach. Its cultural heritage is preserved through museums and monasteries that highlight its historical significance in Greek literature and independence.

The population of the main town was 4,883 in 2011, while the municipality covers an area of 49.898 km2 including several islets. The economy relies heavily on tourism, supported by Skiathos International Airport which expanded its runway in 2013/14 and serves flights from Athens, Thessaloniki, and various European countries. Regular boat services connect the island to Volos and Agios Konstantinos, while internal transport includes buses, taxis, and rental motorbikes, with summer being the peak season for visitors.