Island

Island is one of the five basic land types and provides blue mana, which is required to cast blue spells.

Additionally there is a snow variant, the Snow-Covered Island.

List of Islands
In contrast to other basic lands the islands are ordered by sea or archipelago rather than continent whenever possible.

Grixis

 * Droning Isles

Islands of Azoria
Azoria's ocean featured desert islands until Freyalise destroyed them.

Islands of Cridhe
Cridhe itself seems to be mostly an island. There are other smaller isles though.
 * Southern Isle

Edemi Islands

 * Argenti
 * Kusho

Golthonor Sea

 * Corundis

Jaema Sea

 * Chaza Isles, including Teferi's Isle

Lat-Nam

 * Lat-Nam is known for the College of Lat-Nam.

Spice Isles

 * Tolaria West

Terisiare

 * Lat-Nam, known for the College of Lat-Nam.
 * Videnth

Tolaria

 * Tolaria was known for the academy built on it.

Voda Sea

 * Kish
 * Varnalca

Western Sea

 * Island of Stonehaven

Islands of Kamigawa

 * Otawara, may be considered an island in the sky, rather than in the sea.

Kamitaki

 * The most notable islands are those floating near the Kamitaki waterfall. Minamo was built on one of them.

Islands of Lorwyn
Lorwyn does not have any seas. Instead of islands, the Merrow Lanes supply blue mana.

Islands of Mercadia

 * Saprazzo

Quicksilver Sea

 * Vedalken Spires with Lumengrid

Islands of Rabiah

 * Serendib
 * The Island of Wak-Wak. Home to a tribe of winged folk. Named for a peculiar fruit that grows there. The fruit looks like a woman's head, and when ripe speaks the word “Wak.”

Islands of Ravnica
Ravnica's water supply system also provides mana.

Islands of Ulgrotha

 * Floating Isle

Unknown plane

 * Sevick Isles

Rules
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Trivia

 * The highest rarity an island has ever been printed in was rare in Alpha, as part of WotC's plot to keep players from guessing rarities.