or Sievju (Northern Sami) is the eighth largest island in Norway proper, located in Finnmark county. The 583-square-kilometre (225 sq mi) island is divided between the Alta and Hammerfest municipalities.

Archeological excavations have shown that people have lived on Seiland for over 7000 years. Today, however, the only people on it live in a few relatively isolated areas such as from Altneset to Hakkstabben on the southern tip of the island; Kårhamn on the northwestern side; and the Hønseby, Eidvågen, Fiskebukta, Survika areas in the northern part of the island. In 2006, the majority of central Seiland was designated as Seiland National Park.

There are two glaciers on Seiland: Seilandsjøkelen and Nordmannsjøkelen. The 1,078-metre (3,537 ft) tall Seilandstuva is the tallest mountain on the island. A number of fjords are located on the island including Lille Kufjorden, Store Kufjorden, Nordefjorden, and Jøfjorden.

• List of islands of Norway

• Map of Seiland