'''Gundam Sentinel''' is a photonovel series, one of many Franchise/{{Gundam}} side-stories taking place in the Universal Century timeline. Written by veteran Masaya Takahashi, it takes place during the final phase of ''[[Anime/MobileSuitZetaGundam Zeta Gundam]]'' and the early stages of ''[[Anime/MobileSuitGundamZZ Gundam ZZ]]'' in UC 0088. The story shows TheFederation's efforts to stop an insurrection by elite Federation officers, former Titans calling themselves the New Desides. What's noteworthy about ''Sentinel'' is the debut of prolific mechanical designer Hajime Katoki, the artist behind other iconic Gundams in the franchise such as the [[Anime/MobileSuitVictoryGundam V2 Assault Buster Gundam]], [[Anime/MobileSuitGundamWing Wing Gundam Zero Custom]] and the [[Anime/MobileSuitGundamUnicorn Gundam Unicorn]]. ''Sentinel'' is regarded as one of the most well known Gundam side-stories to have been published, and is usually noted by fans as being one of the most mature stories in the franchise.

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!!Tropes associated with the ''Gundam Sentinel'' are:
* AliceAllusion: ALICE is the AI installed on the S Gundam, and 'she' gradually gains self-awareness over the story.
* {{BFG}}, WaveMotionGun: FAZZ's hyper mega beam launcher, Z Plus and S Gundam's Beam Smartguns. The Z'od-iacok, a Mobile Armor over 200 meters in length, splits down the middle to reveal an absurdly huge beam cannon.
* CivilWar: The New Decides are Titans remnants.
* CombiningMecha: The S-Gundam has a core fighter system and two other flying components, much like the [[Anime/MobileSuitGundamZZ ZZ Gundam]].
* DecoyProtagonist: Ryo is TheHero, but ALICE gets much more CharacterDevelopment...and is the one who actually saves the day.
* TheFederation: Actually being proactive for once!
* FaceHeelTurn: TheFederation send reinforce fleet to Task Force Alpha. Said fleet commander, Admiral Brian Aeno, choose to help New Decides instead.
* FunWithAcronyms: '''Ex'''traordinary '''S'''uperior (Ex-S) Gundam. But that can't compare to "'''A'''dvance '''L'''ogistic & '''I'''nconsequence '''C'''ognizing '''E'''quipment (ALICE).
* VideoGame/GundamVsSeries: Gundam Sentinel will make its debut in ''Full Boost'' and its PS3 port, with the Ex-S Gundam.
* HeroicSacrifice: [[spoiler:ALICE ejects the 3-person core fighter to save her pilots, then shoots down the New Deside's shuttle and the remaining Z'oon with a single shot. Then S Gundam explodes in Earth's atmosphere.]]
* HumongousMecha: It's part of the Franchise/{{Gundam}} series, so yeah.
* {{Interquel}}: Although ''[[Anime/MobileSuitGundamZZ Gundam ZZ]]'' has already started by the time of this story.
* LightningBruiser: The Gundam Mk-V is so fast that it nearly kills its ace pilot Brave Cod the first time he uses. That aside with it Brave becomes a OneManArmy and single-handily wipes out over a dozen mobile suits before Ryu and ALICE finally bring him down.
* MechaExpansionPack: It's this story that really introduces the concept into the Franchise/{{Gundam}} world. The S Gundam has a booster variant, the Ex-S Gundam is basically a stronger S, and the Deep Striker Gundam is the S with so many boosters, fuel tanks, guns, shield generators, and sensor packs added on, it's no longer humanoid, and barely recognizable. The FAZZ is this to the ZZ Gundam, and there's a Zeta Plus variant with heavy boosters attached.
** On the opposite side, the Xeku Ein has at least 3 different mission configurations.
* PunnyName: The villains of the story are a new group of anti-colony soldiers. In the Universal Century, colonies are grouped into clusters called "Sides" - hence, New Desides (De-Sides).
** And then there's the Ex-S Gundam, which set the new gold standard in ridiculously overbuilt mecha designs.
* ShoutOut: Members of New Desides are based on Shinsengumi. And [[TheHero Ryo Roots]] is based on ''Ryo''ma Saka''moto'' (='base', 'root').
* SuperPrototype: Played with - the FAZZ and Zeta Plus Mobile Suits are essentially production versions of the [[Anime/MobileSuitGundamZZ ZZ Gundam]] and [[Anime/MobileSuitZetaGundam Zeta Gundam]].
** The FAZZ was made as a testbed for the [[Anime/MobileSuitGundamZZ ZZ Gundam]]'s Full Armor parts, before Judau got them in that series. In a subversion, the ''parts'' do work as planned, but because the MS itself was gutted for cost purposes (leaving out the FA parts' Anti-Beam Coating, for example), it's a worse unit overall. All three get destroyed on the moon.
** The Zeta Plus, on the other hand, saw considerable service (mostly out of the spotlight) as a good, useful MS. The main S Gundam pilots even use them as trainer units, since they weren't given access to it at the time.
** And then there's the S (Superior) Gundam and it's MidSeasonUpgrade, the Ex-S [[ExactlyWhatItSaysOnTheTin (Extraordinary Superior)]] Gundam, which both Katoki and Takahashi seemed to consider a LightningBruiser GameBreaker. Game depictions range from "very useful" to "better than the [[Anime/MobileSuitGundamCharsCounterattack Nu Gundam]]".
* ThemeNaming: Most of the characters are named after historical figures from the Bakamatsu period of Japanese history. The names tend to use the formula "Given name = direct Japanese-to-English translation, surname = part of the Japanese name changed to a close English homophone" (for example, Isami Kondo -> Brave Cod).
* TheSmurfettePrinciple: The only active female character is ALICE - and even she's S Gundam's AI without humanoid appearance.
* TransformingMecha: The EX-S transforms into a massive spacecraft.
** As the model kits reveal, this is actually done by linking the two fighters formed by the S Gundam with all the excess boosters, similar to the G-Fortress mode of the Gundam Double Zeta.
* VideoGame/SuperRobotWars: The S and Ex-S Gundams both appeared in ''VideoGame/SuperRobotWars4'' as cameo units. Several years after its release, fans hacked ''VideoGame/SuperRobotWarsAlpha 3'' and found half-completed sprites for ''Sentinel'', leading to the theory that it was going to be in but was removed to make room for ''[[Anime/MobileSuitGundamSeed Gundam SEED]]''.
** Hacking of Alpha 2 also shows the same incomplete data which shows that Seed was probably intend to be in alpha 2 and that Sentinel was removed earlier on the line.
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