[[quoteright:330:[[ComicBook/CaptainAmerica http://static.tvtropes.org/pmwiki/pub/images/Screen_shot_2011-01-05_at_10_57_13_PM_2059.jpg]]]]

A SupervillainLair (or a Hero's Headquarters) At Sea! Isolated from any inference of those pesky heroes, our resident baddies can concoct their schemes of world domination in peace. At least until the third act.

Bonus points if the island, or part of it, is shaped like a skull. Extra points for [[VolcanoLair having an active volcano form part of the base]], despite the [[ConvectionSchmonvection obvious problems with heat]] keeping such things from being practical in real life.

A SubTrope of IslandOfMystery.

Often equipped with a DenOfIniquity. See also ElaborateUndergroundBase, UnderwaterBase.


[[folder:Anime and Manga]]
* ''Manga/{{Cyborg 009}}'': An IslandBase showed up in the first episode of the anime. It was used by two {{Mad Scientist}}s like their MadScientistLaboratory.
* ''Anime/MazingerZ''. BigBad and MadScientist Dr. Hell had two {{Island Base}}s: Bardos, an ancient Greek island full of underground mazes and labyrinths where he found an army of HumongousMecha: and Hell Island, an island near from the Japanese coast where he moved later in the series. It was a barren, rocky islet. A low mountain rose in the center, and several giant faces had been carved on its slopes. TheDragon Baron Ashura also had an IslandBase doubled like a CoolShip: the submarine fortress Salude.
* ''Anime/GreatMazinger'': Marquis Janus' HomeBase was at once a CoolShip (it was mobile and could swim or dive underwater), an IslandBase (it was shaped like an island) and a VolcanoLair (an artificial volcano had been built in the center).
* Mewtwo from ''Anime/PokemonTheFirstMovie''. To add to the sinister atmosphere, it was built on the wreckage of the lab - where he was created - that he blew up a few months earlier.

[[folder:Comic Books]]
%% The following {{Zero Context Example}}s have been commented out and copied to Discussion. Please don't add them back to the page unless you add enough information to explain how they're an example of the trope.
%% * ComicBook/{{Blackhawk}} Island.
%% * The Triskileon in ''ComicBook/TheUltimates''.
* Franchise/WonderWoman and her race of Amazons live in a secret island.
* Oolong Island served as a think tank for a number of [[MadScientist Mad Scientists]] in the Franchise/DCUniverse. It is now where the Comicbook/DoomPatrol are based.
* Monster Isle is the base of operations of the Mole Man in ''Comicbook/FantasticFour''
* The ''Comicbook/TeenTitans''' Titan's Tower is on an island.
* Avengers Island, home base of the ''Comicbook/{{New Avengers|2015}}'', which was originally [[NebulousEvilOrganisation A.I.M.]]'s (it was probably called differently then) until Sunspot [[CrimefightingWithCash bought it]]. As in the ''whole organization''. The island base was extra.
** It was originally Hydrobase, an artificial island originally stationed just outside of New York Harbor in the Atlantic. Once the base of operations of ''ComicBook/SubMariner'' foe Dr. Hydro, it became the longtime home base for Dr. Walter Newell, the government operative Stingray. He later leased out space on the island to the Avengers for an airfield after the FAA banned them from flying their Quinjets through Manhattan, and it even served as their temporary headquarters after the Masters of Evil had trashed the original Avengers Mansion, until ComicBook/DoctorDoom's robots sunk the island. It was later salvaged by Namor and Stingray, and eventually relocated to the Pacific, off the coast of California, by the time Sunspot acquired it.
** A.I.M. previously had an island base simply known as A.I.M. Island. They later conquered the small Caribbean island of Boca Caliente. [[ComicBook/IronMan Tony Stark]] tried to get the US government to liberate Boca Caliente from A.I.M., to no avail.
* Cobra had a temporary island base in the first issue of ''[[ComicBook/GIJoeARealAmericanHeroMarvel G.I. Joe: A Real American Hero]]'', and later gained a larger and more permanent one in international waters in the Gulf of Mexico by having the Joes help them ''create'' it. Specifically, they tricked the Joes into detonating a fault line at just the right location to cause enough upheaval to create the island. Cobra even had an army of laywers standing by at the UN to lay their sovereign claim to the newly-formed Cobra Island. It serves as the focal point for several stories, including the original [[EnemyCivilWar Cobra Civil War]].
* In ''ComicBook/TheTransformers'', Shockwave had the Decepticons construct an artificial island base off the coast of Florida, the surface of which concealed the fact that it was also a fully-functional space cruiser. Ratbat later turned the island into a vacation resort called Club Con, even going so far as to having [[TheStarscream Starscream]] appear in a television commercial for the resort. The base/ship was destroyed when the [[AGodAmI Underbase-empowered Starscream]] crashed Scorponok's ship into it.

[[folder:Fan Works]]
* FanFic/DungeonKeeperAmi features several- all of which score bonus points for covering the active volcano, skull-shaped cave, and so on. Just not all at the same time. Zarekos' Islands were riddled with lava-filled fissures, due to the tremendous dark energy contamination, which Ami inherited from him following his defeat. Ami, [[GuileHero naturally]], repurposed them for use as geothermal plants. Later, the battle of Dreadfog Island takes place on an island in a large swamp -- and the island sports a skull-shaped cave incorporated into the fortifications.
* ''Fanfic/SoulEaterTroubledSouls'': Cobra Island acts as one for Medusa in the titular StoryArc. She is huddled up in the snake monolith that takes up most of the island. It is also her place of birth. She's dragged Maka and the others to the island to enact the beginning of a revenge scheme.

%% The following {{Zero Context Example}}s have been commented out and copied to Discussion. Please don't add them back to the page unless you add enough information to explain how they're an example of the trope.
* [[StealthPun Nomanisan]] in ''WesternAnimation/TheIncredibles'', with a VolcanoLair/rocket launch facility, an armed security force, and giant experimental robots designed to kill any superheroes who were lured there.
* Most notable examples are with ''Film/JamesBond'' villains.
** Film/DrNo's Base was on Crab Key, albeit more of an ElaborateUndergroundBase.
** ''Film/YouOnlyLiveTwice''. Blofeld's rocket base is under an extinct volcano on the Japanese island of Matsu.
** Blofeld held headquarters on an oil rig in ''Film/DiamondsAreForever'', technically an island.
** Kananga's island of San Monique in ''Film/LiveAndLetDie'', but it isn't really isolated: it has a tourist trade. Too bad - poppy fields, voodoo totems with guns, [[EnigmaticMinion Baron Samedi]], and a SharkPool.
** Francisco Scaramanga's private island is probably the best example of the trope in ''Film/TheManWithTheGoldenGun''.
** Stromberg's Atlantis base in ''Film/TheSpyWhoLovedMe'' was a giant floating platform.
** Silva's island in ''Film/{{Skyfall}}'' [[GhostTown used to be inhabited]], until he faked a chemical leak, causing the inhabitants to evacuate.
* Dr. Totenkopf's island base in ''Film/SkyCaptainAndTheWorldOfTomorrow'' (2004), complete with robots, [[spoiler:prehistoric animals and a space ship]].
* ''Film/OurManFlint''. Galaxy Island is the headquarters of the Galaxy organization. Features include {{brainwashed}} women, a WeatherControlMachine and an anti-American eagle.
* Captain Nemo's island headquarters in the Disney version of ''Film/TwentyThousandLeaguesUnderTheSea''. Volcanic crater, submarine docking facilities and SelfDestructMechanism.
* ''Film/{{Yellowbeard}}''. El Nebuloso's island, with a castle full of murderous monks.
* The Nazi-controlled island in ''Film/RaidersOfTheLostArk''. Submarine docks, and an area where you can perform Jewish rituals. Watch out for [[YourHeadASplode exploding heads]].
* Baron von Frankenstein's island in ''WesternAnimation/MadMonsterParty''. He has a castle where he performs bizarre experiments.
* ''Film/UndercoverBrother''. The Man (head of a white racist organization) has his secret fortress built on an island.
* In the ''Film/AustinPowers'' series, Dr. Evil once held operations inside a volcano shaped like his head which was key geographical icon on a Caribbean island.
* ''Film/SpyKids 2'' had an island with a hidden base inside the volcano, and gengineered monsters running around.
* ''Film/JurassicPark''. The eponymous amusement park is built on an island, Isla Nublar. ''Film/TheLostWorldJurassicPark'' reveals the primary research facility was on a separate island, Isla Sorna.
* ''Film/BlackDynamite'' faces foes on both Kung-Fu Island and Slave Island.
* Much like its' forebear (see "Puppet Shows" below), the infamous live-action ''Film/{{Thunderbirds}}'' movie has Tracy Island- which looks even cooler in live-action, and now it has two pools (since the film crew realized having a rocket launch next to the main house wouldn't be so good).

%% The following {{Zero Context Example}}s have been commented out and copied to Discussion. Please don't add them back to the page unless you add enough information to explain how they're an example of the trope.
* ''Literature/JurassicPark'', justified as they need it contain all the dinosaurs. Unfortunately it's not as secure as they think.
* Most of ''Billy & Howard'' and ''Literature/{{Duumvirate}}'' take place on one of these.
* "Lincoln Island" is the headquarters of Captain Nemo and the harbor of the Nautilus in ''Literature/TheMysteriousIsland''.
* In ''Literature/TheIslandOfDoctorMoreau'' by H.G. Wells, the eponymous island, where Dr. Moreau performs his experiments with human mutation.
* General Zaroff also had an island base in ''TheMostDangerousGame'' where he hunted... well, you know.
* In ''Literature/The39Clues'' universe: the Ekaterinas had a island base inside the Bermuda Triangle.
** [[spoiler:The Madrigals]] have Easter Island as a base.
** There's also the [[spoiler:Cahill ancestral home]] and [[spoiler:the Gauntlet]], on an island off the coast of Ireland.
* In ''Literature/SoonIWillBeInvincible'', Dr. Impossible used the same island base for 14 years before the heroes finally cracked it. At the climax of the novel, he returns to construct his new DoomsdayDevice in the ruins.
* ''Literature/TheMostDangerousGame''. General Zaroff has Ship-Trap Island, where he passes the time hunting humans.
* In ''Literature/WarriorCats'', [=RiverClan=] makes camp on an island. That is until they are forced to move out of the Old Forest and travel to the lake, where they get a new, not-really-islandy camp. But they make up for it in ''Dark River'' when they [[spoiler:take over the Gathering Island due to their current camp being unavailable to them.]]
* ''Literature/{{Swellhead}}''. The protagonists are sent to investigate strange events on the long-deserted and distant island of Skerra, somewhere on the ill-defined border between Britain and Ireland which for historical reasons even has a monarchy (not that she's ever set foot on the island before now) and is therefore an independent nation. Turns out an ElaborateUndergroundBase has been discovered on Skerra, despite the sheer impossibility of constructing one without vast resources and public knowledge. One which, as they delve further into it, looks increasingly like a classic SupervillainLair... [[spoiler:It turns out the base was constructed by a supervillain in an AlternateUniverse, which is encroaching into our reality.]]
* Goro Yoshida, the eponymous villain in ''Literature/TheManWithTheRedTattoo'' has set up camp for his private nationalist army in Etorofu, which is one of the Kuril Islands, which reside in a disputed territory between Russia and Japan.
* ''Literature/TheDresdenFiles'': From ''[[Literature/ColdDays Cold Days]]'' on, Demonreach has become this for Harry. Its secluded location and powerful GeniusLoci make it far more defensible than his old apartment, but at the same time more vulnerable, as the island is [[spoiler:the site of a massive supernatural prison constructed by the original Merlin to hold some of the baddest bads in the setting, and some of Harry's enemies are interested in setting those baddies loose]]. The isolation from his friends and allies his relocation to the island has caused is also a minor plot point.
* Mystery Island serves this purpose for Cobra in ''Literature/SecretAgentsFour''.
* Deconstructed in one of the Literature/{{Burke}} novels, when the con artist turned private eye uncovers a scam to sell an island as a sovereign territory to the highest bidder. It's a scam because for one thing, [[MightMakesRight none of the world powers would tolerate it]] and so the sovereignty wouldn't be worth the paper it was written on.

[[folder:Live Action TV]]
%% The following {{Zero Context Example}}s have been commented out and copied to Discussion. Please don't add them back to the page unless you add enough information to explain how they're an example of the trope.
%% * ''Series/{{Lost}}''.
* The island of MadScientist Dr. Boris Balinkoff in the ''Series/GilligansIsland'' episode "The Friendly Physician". He has a castle where he performs experiments on the castaways.

[[folder:Puppet Shows]]
* A rare heroic example: Tracy Island in ''Series/{{Thunderbirds}}'', home to International Rescue, and therefore is also an ElaborateUndergroundBase- the pool slides back for ''Thunderbird 1'', ''Thunderbird 3'' launches from within a rounded structure, and ''Thunderbird 2'' launches from inside the mountain. There's even another island nearby which has an underground monorail link to Tracy Island for additional supplies and such.

* In ''[[VideoGame/ProPinballFantasticJourney Pro Pinball: Fantastic Journey]]'', the evil General Yagov operates out of an Island Base as he threatens to [[DetonationMoon destroy the Moon.]]
* The backglass of ''Pinball/AustinPowers'' shows Dr. Evil's volcanic base, with [[DefaceOfTheMoon his face carved on one side of the volcano.]]

[[folder:Tabletop Games]]
* ''TabletopGame/{{Champions}}''
** Adventure ''The Island of Doctor Destroyer''. The title island Destruga holds the secret base of Doctor Destroyer, from which he plans to launch the Hypnoray satellite and MindControl the entire world.\\
In ''Classic Organizations'', after being destroyed in its original location Neutral Ground relocates to this exact island, turning from a fairly posh ''club'' for supers of all kinds into an island ''resort'' in the process. Doctor Destroyer's legacy is brought up in the relevant chapter and used as a plot point in at least one example adventure outline.
** The ''Champions II'' supplement has rules for constructing superhero bases. When choosing a base's location, one option is to build it on an island.
** Malachite, a genetic experiment GoneHorriblyRight, took over a string of uninhabited islands that formerly belonged to Portugal. After the troops Portugal sent to reclaim them were wiped out, the government decided they weren't worth fighting for. Malachite has managed to get them declared a sovereign nation, with him as its ruler, in order to gain diplomatic immunity.
* ''TabletopGame/{{GURPS}} Illuminati''. One potential location for the Illuminati main base is on a private secret island that has been erased from the world's maps. It could even be in the Bermuda Triangle - the reason so many ships and planes have disappeared there is because they got too close to the Illuminati base and saw something they weren't supposed to see.
* ''TabletopGame/HollowEarthExpedition''. If a character has the Resource of Refuge 5 they have a secret island base with everything they could want.
* The Nazis have two of these. Since SpaceIsAnOcean they've built one on Mercury and one in the asteroid belt. Festung Sieg on Mercury. The other is built into one of two asteroids attached to an Erisian spaceship wreck.

[[folder:Video Games]]
%% The following {{Zero Context Example}}s have been commented out and copied to Discussion. Please don't add them back to the page unless you add enough information to explain how they're an example of the trope.
%% * The ''Franchise/JamesBond'' game ''VideoGame/{{Nightfire}}''.
* ''Videogame/FurFighters'' has the last level set in a ''Film/JamesBond'' parody Island base...just off the coast of your hometown.
* ''Videogame/MegaManBattleNetwork 3'', the WWW has their base on an island, across the Demon Waters.
* ''Videogame/{{Metal Gear Solid}}''
** Shadow Moses Island is indeed an island - something the players (and at one point even Snake) needed to be reminded of.
** VideoGame/MetalGearSolidPeaceWalker's Mother Base can become this with time.
* In ''Videogame/PhantomBrave'', [[MessianicArchetype Marona]] lives on an island all to herself, called Phantom Isle, which she uses as a base. The BigBad, Sulphur, also has [[{{Mordor}} an island of his own]], called the Island of Evil, which [[SealedEvilInACan he is sealed in]].
* Franchise/{{Sonic}}
** Prison Island in ''Videogame/SonicAdventure2'', though that's likely based off the concept of Alcatraz.
** The Veg-O-Fortress in ''VideoGame/SonicSpinball'' plays this straight. Built right on top of a volcanic island in the middle of the ocean. Robotnik even manages to incorporate the magma into the base's power systems.
* In ''Videogame/{{Thief}} II: The Metal Age'', the Cetus Project is run from Markham's Isle, a former pirate base taken over by the Mechanists. As you learn when you go there, the administration of the project is a bit complicated, but Markham's Isle certainly fits the IslandBase and ElaborateUndergroundBase tropes.
* In ''VideoGame/TheCurseOfMonkeyIsland'', [[BaldBlackLeaderGuy King André]] operates out of Skull Island. Subverted in that [[spoiler:Skull Island really looks like a giant duck's head, prompting Guybrush to complain "It should be called Duck Island!"]]
* ''VideoGame/EvilGenius'' goes for a twofer, having you [[ElaborateUndergroundBase tunnel into the mountain]] on your "Uninhabited Desert Island of Undisclosed Location (tm)". Midway through you're forced to move islands, because if you're going to use [[KillSat satellite-based]] doomsday weapons it's [[CardCarryingVillain obligatory]] to [[Film/YouOnlyLiveTwice launch them out the crater of an extinct volcano]].
* In ''Videogame/KnucklesChaotix'', Dr. Eggman builds his latest SupervillainLair on an island in order to get himself one step closer to several Chaos Emerald-like objects rumored to be hidden there.
* Used and [[LampshadeHanging Lampshaded]] in ''Videogame/KingdomOfLoathing''; after [[ArchEnemy your Nemesis]] pulls a VillainExitStageLeft after your first battle with them, your class leader says they probably have a secret tropical island volcano lair. Sure enough, you eventually find a map to a secret tropical island volcano lair on one of your Nemesis's thugs and have a final showdown [[ConvectionSchmonvection in the heart of the volcano]], first with your Nemesis's [[SequentialBoss normal form]] and then with its [[OneWingedAngel Demonic form]]. {{Troperrific}}!
* ''[[VideoGame/CommandAndConquerRedAlert3 Red Alert 3]]'' features a secret island base. A secret ''Easter Island'' base. In a volcano. With ''cannons in the Heads''. That shoot ''bears''.
* Dr. Nonookie's Nontoonyt Island lair in ''VideoGame/LeisureSuitLarry II''.
* The headquarters of Cipher, [[IDontLikeTheSoundOfThatPlace Citadark Isle]], in ''VideoGame/PokemonXDGaleOfDarkness''. They even have a machine that generates a constant storm around the island to prevent any unwanted visitors.
* The game ''VideoGame/{{Device6}}'' takes place on a seemingly abandoned one of these.
* ''Legend of Hero Tonma'' takes place on one named Untrodden Island.
* Governor's Island serves as the headquarters of Soviet forces occupying New York in ''VideoGame/FreedomFighters''. Two missions revolve around it, one to infiltrate it and assassinate General Tatarin and the final mission where it is stormed en masse by boat.
* In both ''Rymdjakten'' (''The Space Hunt'') and ''Djuphavsjakten'' (''The Deep Sea Hunt''), the heroes are headquartered on an island solely owned and inhabited by them. They start out rather mundane, with just the home of the person(s) who discovered the central issue of the game and some kind of facility relevant to the game (an observatory in ''Rymdjakten'', a lighthouse in ''Djuphavsjakten''), but by the later portions they include, among other things, training facilities (for astronauts in ''Rymdjakten'', and for divers and dolphins in ''Djuphavsjakten''), construction facilities, laboratories, and in ''Rymdjakten'' two rocket launching pads. In both games, all of this is privately owned.
* The Island of Claymodo in ''[[VideoGame/{{Clayfighter}} Clayfighter 63 1/3]]", home of the MadScientist Dr. Kiln.

[[folder:Web Comics]]
* During the spy spoof arc of ''Webcomic/DanAndMabsFurryAdventures'', [[MadScientist Dr. Jyrras']] [[SupervillainLair base]] is an island with an [[LampshadeHanging extinct]] [[ChekhovsVolcano volcano]]. Filled with orange pillows to simulate lava. It's supposed to be incredibly secret, but the [[GovernmentAgencyOfFiction agency]] has [[http://www.missmab.com/Comics/Vol_456.php detailed plans]].
* Subverted in ''Webcomic/SluggyFreelance'':
-->'''Dr. Steve''': It was your mistake to trespass on... [DramaticPause]... '''the Isle of Doctor Steve!'''
-->'''Torg''': "Isle"? We're in the woods. I never left the mainland!
-->'''Dr. Steve''': Do you know how expensive islands are these days?
* ''Webcomic/{{Narbonic}}'': [[spoiler:The happy ending has this for Helen (and Dave, by extension).]]

[[folder:Web Original]]
* [[http://www.villainsource.com/lairs.html Villain Source]] (formerly Villain Supply) has options of either a Skull Island or a subterranean base on a volcano island.
* ''WebVideo/{{KateModern}}'' BigBad Michelle Clore's evil lair is located on (RealLife) Adak Island.
* At the beginning of episodes of the Dr. Steel show, Music/DoctorSteel's secret laboratory is shown to be on an island. Supposedly this island is located in the Pacific, near Hawaii.

[[folder:Western Animation]]
* Cobra Island in ''WesternAnimation/GIJoeARealAmericanHero'' was introduced in the two-part episode "There's No Place Like Springfield", where the titular town was staged for a FakedRipVanWinkle plot to get Shipwreck to reveal a top-secret formula he'd been entrusted with. In the second season, it became Cobra's permanent base of operations with the completion of the Terrordrome.
* [[MadScientist Dr. Drakken]] and the Seniors both have island bases in ''WesternAnimation/KimPossible''. The Seniors' island was originally just their home, but [[NiceJobBreakingItHero Ron kept comparing it to a typical]] SupervillainLair, inadvertently giving [[EccentricMillionaire Señor Senior, Sr.]] the idea to [[CreateYourOwnVillain take up supervillainy as a hobby]]. It didn't help that the ginormous sunlamp for [[TheDandy Señor Senior, Jr.]] had been causing blackouts across mainland Europe, which is what brought the Seniors to Kim and Ron's attention in the first place. Drakken has several other lairs, but most of them seem to be temporary, as he keeps coming back to his island base.
* Science Island is the headquarters for Jarvis Kord in ''WesternAnimation/BatmanTheBraveAndTheBold''.
* The bunny-shaped island known as Bunny Island is the primary setting for ''WesternAnimation/EvilConCarne''.
* ''WesternAnimation/JonnyQuest'' TOS. Dr. Benton Quest's island of Crab Key. It had dock facilities, experimental labs and a hovercraft.
* ''WesternAnimation/PhineasAndFerb'' has several examples of this:
** Doctor Destructocon (Kevin to his friends), one of Dr. Doofenshmirtz's mentors, had a secret-hideout shaped island with the letter "D" carved into it.
** Doof at one point has an island base on Lake Winemahkateekihaha, complete with a boiling pit of lava.
** He also has a lair on Spleen Island, which was cheap due to old legends about a sea hag that haunts it.
** Later, he rents another cheap island: "Pink Unicorn Island", a big pink island shaped like a unicorn. Doof would have preferred the nearby Skull Island, but it was much more expensive.
** Perhaps the swankiest of all of his lairs is the lair in Montevillebad that he got in an evil exchange program. It comes with all the classic villainous weapons, including a rocket and a catchy theme song.
* [[SesquipedalianSmith Prometheus Black]] AKA, Meltdown has a underground lab on Dinobot Island in ''WesternAnimation/TransformersAnimated''. [[spoiler:Blackarachnia]] moves into it later in the series. [[AllThereInTheManual Apparently]] it used to belong to the government.
* ''WesternAnimation/TheLegendOfKorra'' has [[http://images.wikia.com/avatar/images/8/8d/Air_Temple_Island_overview.png Air Temple Island]] where Tenzin and his family live.
* ''WesternAnimation/SuperFriends'' episode "Too Hot To Handle". Kobar the Solar-Terrarian villain has his laboratory hidden under a volcano on an island.
* ''Young Samson & Goliath'' episode "The Secret of Evil Island". The BigBad Voltor has his base on Evil Island, which is just off the coast of New Guinea. From there he imitates ''Film/DrNo'' by hijacking satellites and using their fuel to power his city/continent destroying missiles.
* ''Grim & Evil'' and related show ''WesternAnimation/EvilConCarne'' featured Hector Con Carne's secret base on ... Bunny Island.

[[folder:Real Life]]
* [[http://www.sealandgov.org/ Principality of Sealand]]: A small former UK military installation used by various groups for a number of different purposes -- from pirate radio station to server room. Declared an independent sovereign state at one point by the owners, which is taken seriously by absolutely nobody.
* World War 2 involved a lot of these especially in the Pacific. Higher-profile ones include:
** The Hawaiian Islands, specifically Oahu and Pearl Harbor as the main headquarters of the US Pacific Fleet
** Fort Drum (AKA the concrete battleship) and Corregidor, guarding the entrance to Manila Bay
** The Channel Islands
** Betio
** Malta (its refusal to surrender to the Axis was a constant pain for Italian and German efforts to keep their forces in North Africa supplied)
** Singapore (UsefulNotes/WinstonChurchill called its loss to the Japanese in just one week the worst disaster in British history)
** Iwo Jima and Okinawa
** Iceland
** Heligoland
** Midway Atoll, barely big enough to host an airfield and a dock (mainly used for resupplying the airfield), best known for being the focus of a pitched four-day naval battle which saw the loss of four Japanese carriers and one American carrier, as well as the depletion of most of Midway's land-based fighter and bomber forces. The small island was a key communications and refueling stop in the American logistics chain linking North America to Australia, New Zealand, and Asia.
** On a larger scale, Japan and Britain themselves (see also below)
* During the UsefulNotes/ColdWar, several U.S. allies acted like these as they hosted US military personnel; most notable were (and still are) the UK and Japan as they are actual islands, as well as Iceland (which didn't and still doesn't have a military when it joined UsefulNotes/{{NATO}}) and Taiwan (prior to the establishing of diplomatic ties between the US and China in 1979). Islands need not be purely geographical, either - Alexander Haig, Secretary of State under UsefulNotes/RonaldReagan, called Israel the US's largest unsinkable aircraft carrier in the Middle East.
* [[http://en.wikipedia.org/wiki/Chagos_Archipelago Chagos Archipelago]]
** It houses a massive US military base at Diego Garcia. It was used for reconnaissance in the 1973 Arab-Israeli war and saw wartime use in the first Gulf War. After 9/11 it was key to the wars in Afghanistan and Iraq. It may house nuclear weapons and may be a "black site" for detaining prisoners. It is more secretive than Guantanamo Bay - which is probably why most people have never heard of it.
** In a true supervillain fashion, forty years ago, its people, the Chagossians, were [[DoomedHometown unceremoniously removed from their homeland]] by a joint operation of the United Kingdom and the United States, and [[YouCantGoHomeAgain essentially left beached in Mauritius as human detritus.]] This was detailed in David Vine's book ''Island of Shame: the Secret History of the US Military Base on Diego Garcia''.
* Not exactly at sea, but during UsefulNotes/TheAmericanRevolution, Francis 'Swamp Fox' Marion had a base on an island in the middle of the South Carolina swamps. It's depicted in the Disney series from the '60s as Snow Island.
* [[http://en.wikipedia.org/wiki/Haulbowline Haulbowline]], which started as a British army base, then became a naval base. Today, the island is home to the Irish Navy.
* [[http://en.wikipedia.org/wiki/Mobile_offshore_base Mobile offshore bases]] are a proposed idea of combining this trope with BaseOnWheels (we suppose it'd then be a Base On Hulls) so as to be able to extend force projection far beyond one's own shores (i.e., the US's) while still remaining in international waters and thus avoid a lot of political problems associated with (American) bases and personnel stationed overseas (e.g., Saudi Arabia, Okinawa).
* Fort Sumter was an island fort protecting the port of Charleston, South Carolina. The island the fort sits on was made from granite shipped from New England, piled high until it was above the waterline, and of course the fort is best known for the Confederate siege and attack which officially began the UsefulNotes/AmericanCivilWar.
* On the topic of the US Civil War, part of the Union's Anaconda Plan was to capture coastal islands to use as refueling ports to support a NavalBlockade of the Atlantic and Gulf coasts.