''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'' and the early stages of ''Anime/MobileSuitGundamZZ'' in Universal Century 0088. The story shows the efforts of TheFederation to stop an insurrection by elite Federation officers, former [[Anime/MobileSuitZetaGundam Titans]] calling themselves the "New Desides". "Task Force Alpha", formed by a conglomerate of Federation soldiers, [[Anime/MobileSuitZetaGundam Anti-Earth Union Group and Karaba]] veterans, equipped with some of the most advanced [[AMechByAnyOtherName mobile suits]] of the era, is sent to quell the uprising.

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/MobileSuitGundamWingEndlessWaltz 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 for having one of the most mature plots in the franchise.

!!Tropes associated with the ''Gundam Sentinel'' are:

* AliceAllusion: "ALICE" is the artificial intelligence installed in the MSA-0011 S Gundam, and "she" gradually gains self-awareness over the story.
* {{BFG}}, WaveMotionGun: FA-010A FAZZ's "Hyper Mega Beam Launcher", MSZ-006A1 Z Plus and S Gundam's "Beam Smartguns". The AMA-100 Z'od-iacok, a [[AMechByAnyOtherName 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 and sympathizers, who're later joined by the Tenth Divisional Fleet that was supposed to assist Task Force Alpha.
* CombiningMecha: The S Gundam has a core fighter system and two other flying components, much like the [[Anime/MobileSuitGundamZZ ZZ Gundam]].
* DecoyProtagonist: Ryo Roots is TheHero, but ALICE gets much more CharacterDevelopment [[spoiler:and the one who actually saves the day]].
* TheFederation: Actually proactive for once!
* FaceHeelTurn: The Tenth Divisional Fleet; said fleet commander, Admiral Brian Aeno, chooses to help the New Desides after a New Desides representative approaches and convinces him to turn {{Heel}}, instead.
* FunWithAcronyms: MSA-0011(Ext) '''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: The Ex-S Gundam was included as a first print-run DownloadableContent unit for ''Gundam Extreme Vs. Full Boost''; it has no pilot for reasons which remain vague and unspecified, but presumably ties into the legal issue surrounding the two versions of the ''Gundam Sentinel'' story.
* HeroicSacrifice: [[spoiler:ALICE ejects the 3-person core fighter to save her pilots, then shoots down the New Desides 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 ''Gundam ZZ'' has already started by the time ''Gundam Sentinel'' begins.
* LightningBruiser: The ORX-013 Gundam Mk-V is so fast it nearly kills New Desides AcePilot Brave Cod the first time he uses it. That aside, the mobile suit allows Brave to become a OneManArmy, single-handily wiping out over a dozen Task Force Alpha mobile suits, ''including'' their three FAZZ units, before Ryu and ALICE in the Ex-S Gundam finally bring him down.
* MechaExpansionPack: This story is the one that really introduces the concept into the franchise. 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 barely looks humanoid and recognizable. The FAZZ is this to the MSZ-010 ZZ Gundam, alongside a Zeta Plus variant with heavy boosters attached.
** In fact, the FAZZ has so much extra armor and weaponry that it can no longer transform/combine. Accounts differ on whether the core ZZ Gundam is still able to split up after jettisoning its armor or if it's custom-built as one piece for added stability.
** On the opposite side, the RMS-141 Xeku Eins has at least 3 different mission configurations.
* {{Portmanteau}}: Overlaps with PunnyName; in Universal Century, space colonies are grouped into clusters called "Sides" - hence, New Desides come from the words "'''de'''cision" and "dis'''sid'''ent".
** The Ex-S ("excess") Gundam, which set a new gold standard in ridiculously overbuilt mechanical designs.
* ShoutOut: All members of New Desides are based on TheShinsengumi.
* SuperPrototype: Played with - the FAZZ and Zeta Plus are essentially production versions of the ZZ Gundam and Zeta Gundam, respectively.
** The FAZZ was made as a testbed for the ZZ's "Full Armor" parts, before [[Anime/MobileSuitGundamZZ Judau Ashta]] got them in that series. In a subversion, the parts do work as planned, but because the unit itself was gutted for cost purposes (leaving out the Full Armor parts' "Anti-Beam Coating", for example), it's considered an inferior unit to the ZZ. The fact all three are destroyed by Brave Cod says something about this.
** The Zeta Plus, on the other hand, saw considerable service (mostly out of the spotlight) as a good, useful unit. The main S Gundam pilots even use them as training 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 naming tends to follow a specific pattern - the first name is translated directly into English while the surname is an English homophone of a portion of the original Japanese name (for example, Isami Kondo -> Brave Cod; ''Ryo''ma Saka''moto'' -> Ryo Roots ("moto" means "base" or "root" in Japanese)).
* TheSmurfettePrinciple: Played with; the only active female character is ALICE, and even then she's merely an AI without a humanoid appearance.
* TransformingMecha: The Ex-S transforms into a massive spacecraft.
** As the model kits reveal, this is 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 ZZ.