There's nothing as good or stealth-focused as Thief, but you could do a lot worse than Chronicles of Riddick: Escape From Butcher Bay, the Deus Ex games, and I guess VTM: Bloodlines can be played as a stealth game as well.

A lot of people like the Hitman games as well, but I've only played a tiny bit of Blood Money, so I can't say for sure.

- Splinter Cell series: the earlier SC games are very similar to the Thief series in that hiding in the shadows and not using weapons are your primary tactics. Both Garrett (Thief) and Fisher (SC) cannot take many hits and thus have to avoid direct contact with the enemy. Both have weapons to defend themselves, but they aren't very effective, especially not if the enemy is alert. And both have a variety of special tools available to them that allows them to get through the levels unnoticed.

- Metal Gear Solid series: mostly console-only. unlike Thief, MGS isn't much about hiding in shadows. It's about hiding everywhere. Instead of using the darkness of shadows to your advantage, you have access to a variety of camo patterns with varying effectiveness in different terrains. You're also advised not to engage the enemy directly. Use stealth instead to eliminate key adversaries silently and then sneak past others.

- Hitman series: even further away from the shadow-hiding of Thief and SC. neither shadows nor camouflage play much of a role here. Instead, Hitman is all about staying unnoticed, not necessarily invisible. Key to success is your ability to acquire and take advantage of disguises.

- Commandos: Strike Force: a tactical military shooter similar to Hitman. Not about hiding in shadows. Instead you use a small team of 3 military specialists to infiltrate German positions, eliminate key targets and gather intelligence. Ability to stay undetected needed.

that's all i can think of right now.

This might be a long shot, but my current playing style of Skyrim gives me some typical Thief vibes. It is way better than Oblivion in the sneaking parts.

Azrael's Tear always gave me strong Thief vibes. It's a first-person adventure game (with free movement, not a Myst clone). You're a high-tech thief exploring a vast system of caves and complexes apparently inhabited since medieval times by immortal knights templar. The type of environments and atmosphere, as well as certain elements of gameplay (no sneaking though) are so familiar I was surprised to learn that AT and the Thief games shared no developers.

Would looove to see that game on GOG some day.

Also, seconding SimonG on Skyrim - the stealth is the best so far in Elder Scrolls games, though it can feel overpowered at higher levels. And there are certainly some familiar atmospheres while exploring the various dungeons and caves (I smiled when I heard bandits, unaware of my presence, mumble nd grumble to themselves just like guards inThief), or even walking around towns at night. Also, Stephen Russell voices a large amount of characters, including a few members of the Thieves Guild ;)

Controversial I suspect, but Metro 2033 has an interesting stealth element to it. It has been suggested that the stealth is broken. I think the correct description would be challenging.

There's a demo for it, though I've not played it so I can't comment on how it illustrates the stealth - also, you will definitely be outright fighting in much of the game. Fairly incredible game, IMO, but I can only take it in small doses - it's tense.

stealth doesn't play much of a role in Metro, though. the mechanic is there, but it's somewhat unreliable, and there are only a few fixed situations in which you get to take advantage of it. in my experience, even a stealthy approach usually ends up in a firefight. or maybe i'm just clumsy.

Metro's not a stealth game by any means.

How the hell can you call Splinter Cell "very similar" to Thief?
SC is to me the opposite of what made Thief great.
It's utterly railroaded, with no room for tactics, exploring and doing clever things whatsoever.
It has behind-the-ass camera view, which means you lose the immersion and reliance on your hearing which made Thief such a great game.

This topic is about "similar games" to Thief, not "stealth games" or "games with stealth".

The Elder Scrolls, Hitman, Splinter Cell or Riddick are NOT similar to Thief, and none have an IA as advanced. It is like if you recommended Duck Hunt to someone who is looking for a game similar to Half-Life 2.
Splinter Cell looks the more similar but it is HORRIBLE and especially linear as hell with only corridors.
By the way, you can play a stealthy character in Dark Messiah of Might and Magic and you also have a rope bow, but it isn't similar to Thief.

As far as I know, there are unfortunately no games similar to the Thief series. Period.
Still, you can enjoy both Thief 1 and Thief 2 (both masterpieces) and a LOT of fan missions (especially T2X) and Thief 3 which is "only" a good game. The Dark Mod for Doom 3 looks interesting but I have not tried it yet.

Splinter Cell has elements that are the same, but at the same time elements are very different...

Both rely on sound, both rely on shadows (in which the player turns nearly invisible if in darkness)... Both have a kind of 'light gem' type interface...

But one relies on more exploration, the other is way more linear... One is primarily first person, the other primarily 3rd person...

One is medievial/victorian, the other is modern/futuristic...

Both can knock out their enemies, but using different ways to do that... Sam Fisher can grab his enemies from behind, Garret cannot... Although Sam is more lethal, and can silently kill his opponents with his hands, and his knife. (Garret gets a silent lethal kill in Thief 3 with his dagger). In previous thief games, Garret was best 'knocking' out his opponents, or simply avoiding them...

Garret has gas arrows, Sam has sticky shockers to quickly knock out an opponent...

Garret has a wider range of arrows to use to explore his surroundings... Sam is pretty limited to a linear path, with the occasional chance to tie a rope down, or cut through cloth...

There is some 'night vision' in both (Thief 2 onward, when he gets the new eye), but that's mostly something Splinter Cell relies on for getting past obstacles/exploring surroundings...

Chronicales of Riddick Butcher Bay/Dark Athena, also relies on pure shadow stealth in places (turn invisible in darkness)... But he's much more brutal, capable of killing his oppents, quickly and efficiently, with any weapon... But huge portions of the game are pure action in lighted areas... However, the few shadow stealthy areas are really well done... But its much faster paced than Thief...

Splinter Cell: Conviction went down the 'faster paced' lethal shadow stealth, more similar to Riddick.... It was further removed from the 'thief' than the earlier games were...

I get the feeling that No One Lives Forever team drew a lot of inspiration from Thief.

It's not actually that similar since it's got a lot more linear feel, you don't use shadows (you do a bit in the sequel), you can (and probably will) kill almost everything that moves and there are a few places where you are forced to play it as a simple shooter. One thing that annoyed me the most when I played the first NOLF is that it's very unforgiving - most often a single slightest mistake makes your enemies sound the alarm, which completely ruins the stealthy mood so expect to load often.

I mentioned the game because it does have some things in common. First of all, it's the atmosphere - NOLF really makes you feel like a 60's spy from a homorous Bond-like universe just like Thief makes you feel like a stealthy thief in a weird medieval/industrial world. You can listen in on some hilarious conversations like you can in Thief if you are stealthy enough. Different types of floor make you sound louder in both games, both are first person, both have a lean mechanism and both have fun gadgets to play with.

In short, I'd call NOLF a Thief/shooter hybrid with some of the gaming's most bizarre situations thrown in. I'm not sure if that's what you were asking, but I thought I'd give it a try anyway.

EDIT: One more thing I forgot - you read a lot of letters, memos, bills etc. which usually tell a funny little background story. Actually, I get the feeling that NOLF has a lot more of those than Thief does.

The closest thing to Thief is The Dark Mod for Doom 3.

The rest are Splinter Cell (very similar gameplay, but present day, linear, and in third person), clones of Splinter Cell and non-stealth games with stealth elements - some good stealth there, but none of them really 'similar' to Thief.

Thank You! I've been trying to remember the name of this game forever. I had it on disc years ago but only played the beginning. It was a pretty cool game. Hopefully, it will show up for sale somewhere and I can finally play it.

You can also try Velvet Assassin, it's not that bad IMO.

Yeah, I had read some awful reviews back in the day, and thus avoided it for years. Then I downloaded it from Amazon last year, and really enjoyed it a lot. The stealth is very specific in what you can do, and the game is very linear, but I had a great time with it in spite of all that. Also, the Amazon d/l version I got has zero DRM, not even Amazon's activation wrapper.

However, I have to agree with Wargnthoi up there: No other game has ever come close to replicating the "Thief" experience. And as far as I can tell, no other game has even tried. I've looked far and wide. This lack of imitators baffles me.

Your best bet would be to locate the best fan-made missions, or sets of missions.

And don't forget "T2X: Shadows of the Metal Age" for Thief 2: A fan-made mission pack that very nearly equals the original games in terms of quality. I was seriously impressed. It is excellent.