[[quoteright:191:http://static.tvtropes.org/pmwiki/pub/images/UltramanGaia_2937.jpg]]

'''''Ultraman Gaia''''' is a {{toku}}satsu series that aired from September 5, 1998 to August 28, 1999 on TBS. It is the thirteenth entry in the ''Franchise/UltraSeries'', with ChiakiKonaka as head writer.

''Ultraman Gaia'' takes place in yet another universe, one that is totally different from the world of the original Ultramen(the inhabitants of the Land of Light), as well as the world of ''Series/UltramanTiga'' and ''Series/UltramanDyna''. It is the first series to feature two Ultramen as the main characters -- Ultraman Gaia and Ultraman Agul, [[RedOniBlueOni both having conflicting philosophies in regards to defending the Earth]] from a mysterious, malevolent and extremely intelligent cosmic entity.

The first half of the series explores the growing tension between them, and their eventual clash. The second half has them reconcile their differences so they can defeat their common enemy.

----
!!''Ultraman Gaia'' provides examples of the following tropes:

* AIIsACrapshoot: The CRISIS integrated-circuit supercomputer. Although it manages to predict in 1997 that Earth would be annihilated by something known as "Kongenteki Hametsu Shorai Tai" (Entity that Brings Radical Destruction), it calculations had been sabotaged by the monster Zorlim, and it gets infected by a computer virus in episode 27.
** Averted by Gamu's PAL, which works perfectly as an auto-pilot and even survives being shot down.
* AllYourBaseAreBelongToUs: Hiroya invades Arial Base with surprising ease in episode 18, by taking advantage of Agul's ability to teleport through certain materials and just transforming back to save power.
** Later, in episode 27, a computer virus manages to completely override XIG's computer systems.
* AlternateUniverse: From the Showa-era Ultras (''Series/{{Ultraman}}'' to ''Series/UltramanEighty'') and [[Series/UltramanTiga Tiga]]/[[Series/UltramanDyna Dyna]]'s universe.
* AntiHero: Hiroya Fujimiya / Ultraman Agul is a Type V. Though he occasionally helps Gaia in certain battles, he reminds Gaia that their alliances are merely because it is his duty to protect Earth (the planet, not the humans on it) due to his [[HumansAreTheRealMonsters belief]]. [[spoiler:After suffering an [[HeroicBSOD Anti-heroic BSOD]] in episode 26, [[PutonaBus he is presumably killed by Zorlim and doesn't appear]] until ten episodes later, and only leaves this trope for good when he finally gets his powers back in episode 41.]]
* AttackOfTheFiftyFootWhatever: It's an Franchise/UltraSeries. Standard procedure.
** The nature of the series means that the threats tend to be towards Earth rather than just humanity (there aren't any serious invasion attempts in the show), and so the 'Whatever' tends to be a few orders of magnitude larger than just 'fifty feet' [[DarkerAndEdgier far more frequently than is comfortable]].
* {{Badass}}: Gaia and Agul, naturally.
* BadassBookworm: Gamu Takayama. A scientist who can assume a superhero form to fight monsters. Hiroya Fujimiya too, but Gamu is the more obvious example. Something of a subversion for the franchise, as this is only time TheSmartGuy(s) transforms into the Ultra.
* BadassCrew: XIG. The individual Teams even more so.
* BashBrothers: Gaia and Agul, [[spoiler:after solving their differences]].
* BigBad: [[spoiler:Zogu]]
* BladeBelowTheShoulder: Agul's Agul Blade
* BlobMonster: Apatee (episode 3), Algyuros (episode 16) and Meemos (formed from the DNA of previous two in episode 27).
* BoisterousBruiser: Team Hercules. Their MO boils down to 'drive up to the Kaiju and shoot it'; when that fails, it becomes 'fight the Kaiju on foot'.
* BusmansHoliday: Gamu gets one in episode 5. He is ordered to take a day off and go inform his parents in Chiba that he's joined XIG (and quit the university). On that same day, the monster Bokurag appears to attack that very place.
* TheCape: Ultraman Gaia
* CriticalAnnoyance: In a subversion of the trope as it usually plays out in the franchise, the Life Gauge on Gaia and Agul's chests begin blinking only when they run low on energy.
* {{Crossover}}: In every movie Gaia appears in.
* DarkerAndEdgier: Compared to both [[Series/{{Ultraman Tiga}} its]] [[Series/UltramanDyna predecessor]] and most of the ''Franchise/UltraSeries''. It's never something you couldn't show to children, but the threats tend to be on a ''planetary'' scale on a regular basis.
* {{Deuteragonist}}: Hiroya Fujimiya / Ultraman Agul
* TheDollEpisode: Episode 19 -- Lilia's Maze.
* EverythingIsOnline: XIG's control systems, which is why a [[AIIsACrapshoot rogue computer virus]] was able to [[AllYourBaseAreBelongToUs severely disrupt the Aerial Base]]. After Atsuko manages to eliminate it, the virus went to Geobase, [[FromBadToWorse merged itself with the DNA samples of previously defeated monsters Apatee and Algyuros and transformed itself into an imitation of Ultraman Gaia]].
* EvilTwin: Played with by several [[MonsterOfTheWeek Monsters of the Week]] in this series.
** Episode 3 has Gaia fighting against Apatee, said monster has a Life Gauge identical to Gaia's, even imitates Gaia's fighting pose at the start of their battle.
** Later on in episode 16 Algyuros transforms itself into an imitation of Ultraman Agul, but with [[RedEyesTakeWarning red eyes]] and a [[SlasherSmile creepy smile]].
** Then in episode 27, Meemos, a monster which contains the DNA of both the previously mentioned monsters, manages to transfrom itself into an imitation of Ultraman Gaia Version 1.
** Yet another imitation of Ultraman Agul appears to fight Gaia in episode 38 after being summoned by the Queen Mezard.
** The most obvious example - Episode 42: Gamu vs. Gamu.
* GadgeteerGenius: Gamu. He designed the [[TransformationTrinket Esplender]], as well as the repulsor lifts that allow Aerial Base and the XIG fighters to defy gravity.
* {{Kaiju}}: Two types. Those from Earth and those from space.
* MeaningfulName: Ultraman Gaia appropriately gets his name from the [[http://en.wikipedia.org/wiki/Gaia_Theory Gaia hypothesis]], which states that the Earth functions like a giant, living creature.
* MonsterOfTheWeek: Following the tradition of a typical ''Ultra'' series.
* TheMovie: ''Ultraman Tiga & Ultraman Dyna & Ultraman Gaia: Battle in Hyperspace'' (1999) and ''Superior Ultraman 8 Brothers'' (2008), both [[NonSerialMovie unrelated to the series' storyline]].
* MundaneUtility: The nature of Gaia/Agul's powers and transformation means that Hiroya can easily infiltrate the Arial Base control room and lock everyone out... and Gamu can just teleport in as Gaia (episode 18).
* MythologyGag
** In episode 45, Blitz Blotz, a black and white avian monster destroys a G.U.A.R.D. base resembling the [[Series/{{Ultraman}} Science Patrol headquarters]].
** Before Gamu using his Esplender to store Gaia's essence, Gamu transform into Gaia with photoelectron tube, mirroring [[Series/{{Ultraman}} Shin Hayata's transformation as Ultraman via Beta Capsule]].
** Episode 18 shows that there's apparently a restaurant/cafe called '[[Series/UltraSeven Eyeslugger]]' somewhere in this universe's Tokyo.
* NextSundayAD: The series is set in the year [[TurnoftheMillennium 2000]], with flashbacks to key events taking place in the late [[TheNineties 1990s]].
* PeopleInRubberSuits
* RedOniBlueOni: Gamu Takayama / Ultraman Gaia and Hiroya Fujimiya / Ultraman Agul. Just look at their respective skin colors when they are Ultramen.
* RewindReplayRepeat: Happens a few times with Kenji Tabata and his videotapes.
* RunningGag:
** Every time Team Hercules lands in the Stinger, they knock at least one bicycle over.
* ScienceHero: Gamu Takayama, who gets help from his friends at Jonan University too.
* ShoutOut
** [[ActionGirl Catherine "Cat" Ryan]] dresses up like [[Franchise/{{Terminator}} Sarah Connor]].
** Episode 42 has Gaia engaging in a swordfight with [[MonsterOfTheWeek Bizorm]] using [[Franchise/{{StarWars}} laser beams]].
** Episode 5 feature monster call Bokrug. The direct-to-DVD ''Once again Gaia'' has a flying monster called Byakhee and underwater city Celephais. Yeah, tributes to Franchise/CthulhuMythos.
* StoneWall: The Stinger, often used by Team Hercules, is unusually tough and reliable, but slow as molasses.
* SuperpoweredAlterEgo: Averted, surprisingly. Gaia and Agul ''are'' Gamu and Hiroya, imbued with power and in giant form.
* SuperMode: Gaia's Supreme Version and Agul's Version 2.
* SymbioticPossession: Between both Ultras and their human hosts. Par for the course for Ultramen (unless they [[Series/UltraSeven make]] [[Series/UltramanLeo them]] [[Series/UltramanMebius up]]) - but subverted here as it's the ''humans'' who take over the giants' forms.
* ThemeSongPowerUp: Happens in episode 49.
* TransformationTrinket: Gaia's Esplender and Agul's Agulator.
* TokyoIsTheCenterOfTheUniverse: Subverted. Despite most monster attacks taking place in Japan, Gaia has fought monsters in Canada, United States and Germany.

----