Wizardry 1-5, probably most of the Japanese wizardry games.
System Shock
Fear & Hunger
Baroque
Darkest Dungeon

Random last one I remembered but Descent to Undermountain!

Ys Origin is my personal favorite

Enter the Gungeon may be a strech since a ton of roguelikes could fit that same description, but still, I think it's worth mentioning.

Oh yeah, Ys Origin is perfect if you want a huuuge dungeon

Does Etrian Odyssey count also?

think these all count (been a while for a few)

rogue
nethack
eye of the beholder / eye of the beholder 2
dungeon rats
das geisterschiff
elminage original / elminage gothic
paper sorcerer
tower of time
diablo (1)
dungeon encounters
system shock 2
exanima
depths of fear knossos
arx fatalis
ultima underworld

ss2 might not count cos you briefly leave the ship (dungeon) to go to another smaller ship (dungeon) now that I think about it

A teensy bit of a stretch but Persona 3. Tartarus is just one big mega-dungeon which you spend the whole game traversing and you only leave the surrounding area of Tartarus in the regular world once.

Great list idea! Some suggestions:

Bastion
Dark Cloud

It's been a while since I played both but pretty sure they are one dungeon only.

Trails in the Sky the 3rd.... maybe... feel free to disagree

dcss, and probably most traditional roguelikes that are dungeon crawlers apply here

I think the first Megaten fits. Although it'd be the same as Metroid or Ys Origins - a giant dungeon complex that contains different dungeons that look different between them.

@DeemonAndGames A ton of roguelikes do fit this descriptor, and I personally am not interested in the rogue-like side of exploring a megadungeon, but I will add them for people who do want that.

@FallenGrace Looking those up and I think they are "multiple dungeons". I think Bastion is more about traveling across the land more so than traversing a dungeon, and Dark Cloud has multiple villages from what I can see.

@Lot0 yeah mutiple biomes in one megaplex is fine I think. Im not sure on SMT because just looking at the like "dungeons" in game they all seem like distinct locations rather than exploring multiple floors on 1 location.

@Snigglegros Don't mistake SMT with the first Megaten from 1987. That's the one I was referring to.

off the top of my head, An Elder Scrolls Legend: Battlespire
my bf tells me Dungeons of Dredmor
Kingdom Hearts Chain of Memories fulfills the general idea as a high concept but in practice it probably doesn't count for what you're actually looking for, ymmv
also weirdly I think Yu-Gi-Oh! Monster Capsule GB fulfills this without any major asterisks; the whole thing takes place in Kaiba's "Duel Tower" which is in reality a sprawling (by GB standards) multi-floor/multi-biome dungeon Yugi must go through to save his friends while dueling people in a tournament along the way
maybe I'll think of more later

No worries, I wasn't sure as it had been a while...

Unexplored (a single, several-floor proc-gen dungeon a la Rogue)
Hammerwatch (there's two campaigns, the first one is entirely one dungeon, the desert one has a hub city but still pretty much takes place in a single dungeon iirc)

Maybe a reach but how about God of War? After the prologue you spend like 90% of the game in Pandora’s Temple looking for the Box

@HunterMask yeah I think that's a little much of a stretch. I don;t really think it has that "exploring a dungeon vibe"

The Dungeon of Naheulbeuk : The Amulet of Chaos

definite fits:

quantum theory
ffx-2 last mission
iron angel of the apocalypse
pandora's tower


depends on what qualifies as a dungeon:

i have no mouth and i must scream
resident evil
alien isolation
castlevania
metroid
prey 2017 (similar to system shock)
ico
the last guardian
resonance of fate

loose consideration:

dead rising (enclosed in an abandoned mall. game takes place almost entirely in the mall)
mega man legends (the entire dungeon/cave system is interconnected and huge)
tecmo's deception (you're uh, managing a mega dungeon. you also walk around in it)
salamander (game takes place inside a giant creature)
abadox (clone of salamander)
bomberman act zero (more of a lore thing than anything because you're constantly being moved up floors in a huge tower)

deathtrap dungeon!

Underworld Ascendant
Slay The Spire

Recettear also has one major dungeon

I don't think Darkest Dungeon should be here, 5 bespoke dungeons as well as the town hub and a few special event missions (bandit raid, big ol' dang bird) that take place in their own locations

@chandler From reading I have no mouth and must scream synopsis, that seems more like individual dungeons Mind Dungeons for each character. While in the physical plane they could be in a dungeon I guess, I don't that really evokes the feeling.
A couple of those (Prey/RE/Alien Isolation) mechanically take place in 1 location, and could be dungeons in a extrapolated sense, but I think I want like more grounded dungeons/towers. I updated the description to better fit (I think that's what I want anyways, trying to find a better reason why those arent than just saying "Vibes are wrong".)
I was trying to think about Dead Rising, and at first I thought about it being flat, but I don't think I can say no to a dungeon just because it has 1 floor. I think a better reason is there is no clear end location to go to when you first dip into the Mall (i dont think). Like Frank isn't there to find the treasure/boss room, and the map is a circle.
Castlevania I've been debating a while, cause I do think castles can fit the "Dungeon", there is a end boss to defeat. I guess I'll put it cause I really can't see why not.
Ico/Last Guardian I don't think I can get a good bead on, but I;m leaning no(?).
Where are the places you can go in Resonance of Fate? From what im gathering it appears to be a big city type place with a tower, but you explore the city a bunch? Can you go outside the city?
I think i'll add tecmo cause I think dungeon management games should count(?)
I don't think Salamandar/abadox fit because of the gameplay style. That shoot em up style just doesnt sit right, but I would fuck with a aliving creature dungeon.
I think i;ll add bomberman act zero cause its funny

@SkeletonHouse Yeah I was talking about it with a friend and they also kind of disagreed, but I was going with the dungeons are like close enough to the town where that could technically be 1 big dungeon. I think ill just get rid of it though.

ihnmaims is more like, "the entire world is now a giant dungeon". it's been completely destroyed and engineered to torture the protagonists by AM, a giant megacomputer

prey/alien isolation i also seemed iffy on. on a similar basis i'd also recommend against system shock here - that game takes place in a space station and prey 2017 is directly inspired by it

dead rising i wouldn't add based on your criteria. it isn't a dungeon - it's just an enclosed location

in your shoes i would probably sooner add metroid than castlevania because "exploring underground caves on an uncharted planet" is more dungeon-like than getting to the top of a castle

ico is a game where you are trapped in a castle and you need to break out. the last guardian is a game where you are at the bottom of a giant ruined tower and you need to find a way out

resonance of fate takes place entirely on a tower. it's like if ff7 was entirely midgar, basically

regarding deception: i think it has a different take on the whole dungeon management thing especially because you're still like, walking around it in first person all the same. it's just that you're planting traps and manipulating the hero types trying to break in to kill you. a similar concept is the "holy invasion of privacy badman" series, but those games are very impersonally about dungeons. you basically carve paths out of dirt to facilitate the lives of your minions and try to bait heroes into mazes where they get killed before reaching you

Sounds like Super House of Dead Ninjas?