What are the scariest horror movies?

It Follows. It isn’t the best horror movie, but the premise is one of the scariest for me. An entity that is inevitable, and you cannot get away from no matter what you do or where you go. It’s always there, walking towards you.
- I agree that the idea of it is terrifying. I just feel like they executed it poorly in the movie. They somehow made it a little hokey.
  
  Thank you! It felt like they could have done so much with it but turned it into the usual monster movie. The first appearances where "it" could be anyone were the best.
- Is the entity an immortal snail?
  
  Just sprinkle some egg shells around ya
- I love this film. No real jump scares or anything, just this unsettling idea that lingers with you long after the film has ended. For a few nights I was very conscious of where my exits were at any given time
- It Follows is definitely one of the best horror movies regarding suspense and general feeling of ... gloom?! Eireness?! Futility?! Darkness?! Whatever it is, I love it!
  And the (potentially) underlying message is powerful.
  
  And the (potentially) underlying message is powerful.
  So this I didn't get. Dangers of STDs?
- There is a single scene in this movie, involving a door, which makes my skin crawl harder than just about anything I've seen in film. It's also sadly spoiled slightly in one of the trailers, so I'd avoid those, but even if you do see it it's still impactful.
  The rest of the movie is a solid 7-8/10 that does a great job of referencing a lot of classic horror.

There is a particular type of emotion which "The VVitch" and "Hereditary" get absolutely perfect. It's actually not really my favorite type of movie; it's not particular scary, per se, but it is just some stuff that is really awful that you don't want to see. If you don't want that, they may not be good, but if you vibe with that particular emotion they are hard to beat for it.
The HBO "Chernobyl" miniseries is absolutely straight-up horror. It has pretty much all the elements of a perfect horror movie, except it's (with tiny exceptions and artistic licenses) all 100% true.
"As Above, So Below" is fairly good "normal" horror of a fairly unspicy flavor.
That's honestly all I can think of that really does it well. Horror books in my experience are far better. "The Shining," "Pet Semetary," "Night Shift," and "Skeleton Crew." Also lots and lots of HP Lovecraft; the "Dunwich Horror" collection is wonderful.
Hope this helps.
- There has got to be a term for the particular type of ... restlessness(?) that movies like VVitch and Hereditary inflict. It's not exactly horror, but a distinct discomfort that I can't quite name. Talk To Me also got close for me but not as far as Hereditary.
  
  I would say the term “dread” comes close for me.
  
  This is why I liked Longlegs so much. Not scary, but damn that movie made me uncomfortable.
  
  Suspense?
- Oooh yes. I'm with you and the other commenter that that particular feeling of dread is really really great. Hereditary, Midsommar, and VVitch definitely all fit that bill. I've heard the same for Lights Out, so I'm going to give that a go too.
  Also Chernobyl is so so good. I've seen it a few times now and oof.
- All films from Robert Eggers with his debut "The VVitch" and Ari Aster with its debut "Hereditary" are highly recommended although not all films are 100 % horror movies.
- How's Chernobyl scary? It's just life man

Not a horror film per se, but definitely leaning that way:
The original 'ALIEN'.
The building of tension throughout the entire movie is brilliant.
- Alien is definitely a horror film. In fact it was originally marketed as such
  
  I know it scared the shit out of me the first time I saw it.
  I was 15 and my family rented it. So I didn't get to see it in its full theater screen glory. Just a 25" console TV from a well worn VHS cassette where the top 25% of the screen was wavy.
  And yes, I'm old.
- I think Alien is a great movie (and definitely horror), but whether it scares modern audiences is pretty hit and miss. It's very slow paced and while I love the practical effects, the alien looks downright goofy in some scenes. I certainly don't find it scary having seen it, and new viewers I've shown it to usually aren't that scared unless they're self-identified wimps when it comes to horror. Aliens is scarier I think, even though it's more action than pure horror.
  Same goes 10x for The Exorcist. It tops a lot of "scariest movie ever" lists online, but watching it today is more comical than anything. I think you have to be scared of demonic possession actually happening IRL to get scared by that movie.
  
  the alien looks downright goofy in some scenes

If you like the supernatural/demon ones, check out The Autopsy of Jane Doe. I loved it, the tension is absolutely perfect and a fantastic cast to boot.
- Added to the list!
- Ooh great call

Drag Me To Hell was surprisingly scary and also just a good movie.
- So fun! I loved Drag Me To Hell.
  
  Know what it's actually about?
- Adding to my list, thanks :)

I don’t consider many horror movies genuinely scary. The ones I have, at various times in my life, been actually in some way frightened (or at least shook) by, in no particular order:
The Exorcist (The Version You’ve Never Seen)
Hereditary (a masterpiece in my opinion. Free upvote literally every time I see someone recommend it)
Blair Witch Project
Paranormal Activity
Ouija: Origin of Evil
It (miniseries got me as a kid but Chapter 1 is good too)
Lights Out (not the entire movie but it has its moments and overall a good style)
Candyman (original)
Poltergeist (original)
Autopsy of Jane Doe (another poster reminded me of this one!)
The Taking of Deborah Logan (for like one scene but IYKYK)
The Dark and the Wicked
The Orphanage
Terrified and When Evil Lurks were both solidly unsettling at least
Event Horizon (though I know you didn’t like this one)
Conjuring 1-2 and Sinister too, all at least solid spookies.
Note that this does not mean these are the only GOOD horror movies. There are LOTS that I consider masterpieces that just aren’t strictly all that scary.
- Blair Witch
  
  It hit on a very specific fear of mine that I have difficulty putting into words. The fear of developing a fear or maybe the fear of becoming superstitious?
  
  It’s an interesting movie. In a lot of ways it’s annoying or underwhelming and not much actually happens, but I actually loved the ending.
- Can I ask what scared you about The Exorcist? Assuming you watched it as an adult and are not highly religious; otherwise I get it. I watched it for the first time a few years ago after seeing it regularly called one of the scariest movies of all time -- maybe my expectations were too high but I found it almost comical.
  
  I saw it when I was in my early twenties and I’d never seen it before. But tons of pop culture had made jokes of everything in the movie and I expected it to just be a laugh.
  The film did such a good job developing dread and helplessness that I forgot all about the jokes.
- Oh I agree that they're not the only good horror movies, there are so many out there that are good in other ways and many of which I absolutely love. But I'm really just looking for that something to keep the lights on at night, lol.
  Thanks for the list! There are a few I haven't seen in there, I'll give them a try :)
  
  I’d love to hear your thoughts on anything new you try! Or if you have opinions on items in my list, even.

The original Candyman.
Everything about it is excellent and holds up even now. The musical score is exceptional.
Don't bother with the reboot. It has a message it's trying to send, which I get, but they've done it to the detriment of the horror. Something could've been done with the premise but they fell short.
OG all the way.
- This movie is incredible. The moment when the protagonist climbs through the wall and it turns out to be a mural is permanently imprinted in my mind. I don't know if the pure horror elements work that well, honestly, and I don't really find it that scary as a result, but it's a fantastic and unique movie with a bold vision and strong themes.

Horror movies don't scare me, but Hereditary was the one movie that made me come close to experiencing genuine fear from watching a movie.
- Meh. Towards the end I was laughing at the Spiderman bit. Hilarious.
  
  The movie started insanely strong but fell off just as hard, at the halfway point at the latest it was just bad
- When people say this they're just talking about the one single moment in the first half of the film, right? The rest of the movie was interesting but idk about scary.
  
  You mean after like 15 minutes?
- Tell me about it. Horror movies are such a snoozefest but Hereditary gave me the creeps.

I’m pretty dead inside so not a ton can get through in the horror department, but I always thought 28 Days Later and 28 Weeks Later did a fantastic job making zombies a bit scary again.

Annihilation is great cosmic horror.
- The scene with the bear…

If you want something a bit different, seek out Threads. It's on the Internet Archive (here, in fact)
Not a traditional horror film at all, it's set in the north of England in the early 80s (depending what n where you're from, the accents might prove a challenge!) and shows the ordinary people of a small city gradually coming to terms with escalating tensions between East and West, which result in all out nuclear war.
And then we get to see the actual on the ground nightmare that that would be. Not in a showy Hollywood way but in a grim, horrifyingly real feeling gritty British drama way. Bleak isn't the word.
It's something that's never quite left me since I saw it for the first and so far only time some years ago. Truly disturbing, and not fun at any point after things start getting serious. Brilliant though.
- I've seen this one recommended a bunch, but I always thought it was a documentary. Interesting. I'll give it a watch.
  
  Some of it is presented like a documentary, but most is done as drama. Hope you enjoy it (although enjoy isn't the word!)

For me The Shining is one of the scariest movies and The VVITCH also comes really close to that feeling. For different types of horror I'd also recommend La Piel que Habito, Shutter and The Haunting of Hill House (the show).
And if you get the chance try the book version of Let the Right One In. It's much better than the movie and more of a horror imo.
- Love The Shining! Stephen King actually wasn’t a fan of the movie, but I think it’s because it’s based on some of his own struggles with addiction.
  
  It's very different from his book but they're both great on their own.

Not sure how great it holds up today since it was a while ago I watched it last, but The Thing is for me still one of the best ones.
- While a great movie, I wouldn't necessarily call it a horror. The Thing is a suspense movie based on mistrust and paranoia, but I wouldn't call it scary.

Cloverfield - not sure if thats horror
Frailty
Insidious
As a kid i loved the early Jason and Freddy movies.

Perfect Blue
I absolutely love and hate how they mess with your perception of not only time but what's real because I could see myself in situations where I couldn't tell you how long has passed and/or having to question if what I'm seeing is real or not.
- Thanks for reminding me about this movie. Been meaning to watch this for a while.
  edit: it was really good!

Some suggestions from my side - in addition to many already posted suggestions I would add to my list as well:
The series Twin Peaks (all three seasons plus the feature 'Fire Walk With Me') is not 100 % horror but it has it's tense of mystery and some scary scenes as well
Don't Look Now from 1974 - a classic mystery drama with great Donald Sutherland in the leading role - also more mystery/suspense than horror
IT (reboot) - still scarier than the Terrifier movies which are more slasher / fun-splatter
Quarantine - until I saw the original 'REC'
Schock - Italian horror movie classic
Barbarian - I expected different but I was surprised in a positive way

I enjoyed High Tension.

As Above, So below is reasonably solid
There's a bit of a Mary Sue issue but otherwise good.

The latest one that got to me, was "When evil lurks" (Cuando acecha la maldad). A pretty fast-paced horror from Argentina.
- And my favourite one before that was "The Descent". A claustrophobic horror following a group of cave explorers.
- This movie was so good until the end. I was like "oh, ok.".

I liked Noroi: The Curse.
No jumpscares, but really quite unsettling

Rec (2007) and Climax (2018) are some of my personal favourites that have scared me to some degree
- The original Rec and Rec 2 are great, the third movie was terrible and the Hollywood remake of the first Rec is a disaster.

What I've learned from this thread as someone getting into horror again is that I really need to watch Hereditary and the original Candyman. Might just bookmark this for all the great recommendations. Only hard part is that my partner isn't into horror so it's hard to watch them.

If you are a muslim then dabbe 3. It is the most terrifying movie i have ever seen.
- Why is it only scary for Muslims?
  
  It has a lot of black magic and jinns in it, which are quite consistent with islamic mythology. The horror hits you differently if you have heard stories about it in your childhood.
  I mean for me, i can shrug off almost anything with "yeah right" but when it comes to islamic mythology, i kinda believe in it so it's more scary.

The Borderlands (2013) is a great found footage horror film with a unique twist on the genre. The ending was particularly horrifying to watch, and I don't normally find horror films scary.

Many other good ones have already been mentioned, so I won't repeat those titles. But "Suspiria" (2018 edition) definitely deserves a mention. The ending is just ... well, clearly somebody amongst the original writers had some issues regarding reproductive systems ... but the other 98% of the movie feature brilliant suspense & eiriness at all times. And Tilda Swinton is simply to-die-for in it. ;)
- The original is a significantly better film.

A Tale of Two Sisters is one of the only movies that has genuinely scared me, some great scenes in it.
- Saw that at the cinema when I came out, scared the hell out of me!

The Ring remake (not the original Japanese one) takes the cake for me. I couldn't sleep the first nor second nights I saw it.

so many recommendations already said and im sure many more to go.
Three that i didnt see mentioned that i enjoyed were:
Martyrs- French Version The Visit Session 9
Scenes from martyrs have been memed out of context so i think its fairly familiar. i hadnt watched it until recently and i think one time through was good enough for me. i’m not into a lot of torture style suspense.
The visit was particularly scary for me because If you’ve ever been in that scenario of being dropped off with familial strangers those initial reservations you have running through your head do make you uncomfortable and blossom into horrific thoughts. in the case of this movie a bit more so ;)
Session 9 i watched during the golden age of netflix. it isnt amazing but it was enjoyable.
- I agree with Martyrs. Will never watch this again. Fuck this.

I absolutely love horror movies and have a long list of fantastic ones but not very many of them actually scared me. Most of them have been named already but two I didn't see were The Babadook (2014) and surprisingly a Netflix movie called His House (2020) was actually awesome. One of my favorites in the last few years.
- Yeah I actually think that my favorite horror movies are the ones that get me asking questions, rather than being scared. I like being intrigued by the evil, like in Smile (until the twist at the end, it was a perfectly good psychological horror that did not need a monster)

“Host” fucked me up and is the reason I don’t watch horror movies anymore. I’m a huge baby though.

I really enjoyed Pandorum and The Babadook.

I don't get scared easily, but Kothanodi had me watching through my fingers. It has four vaguely connected stories, and two of them are very fucked up. There's a decent amount of infanticide and other atrocities inflicted on minors, so be warned if you have any childhood trauma.
Also by the same director, the movie Aamis is about cannibalism acting as a replacement for sex. It's pretty fucked up as well.

can recommend Coherence

May be Apostle? It's one of the memorable ones among recent horror.

My vote goes to The Vanishing (1988).

Megan is Missing (2011) is one of the most horrifying films I've ever seen. Fair warning though, the last ten minutes are excruciatingly painful to watch. It is not for the faint of heart.
In the gore porn genre Cannibal Holocaust (1980) and Hostel (2005) are vile, but so pointlessly gorey the actual horror (the brutality of men) is almost entirely lost.
Funny Games (1997), or the 2007 American remake for those who don't love subtitles, is another unnerving portrayal of ultra violence. It's not gore porn, but is graphic. The original version's pacing will make you squirm in your seat.
Hush (2016) and Creep (2014) are two of my movie-night-with-friends films. Still very much about the human monster, but not overly graphic and prefers to build by making the viewer a partial participant. You have to be a certain level of broken to enjoy some of the others on my list, but these two are disney movies compared to Cannibal Holocaust.

Soft & quiet.
Humans are a terrible thing
https://m.imdb.com/title/tt14557188/

Talk To Me. I would also say Sinister and The Conjuring are my favorites, and I also struggle to find scary movies that genuinely scare me. Watch this alone in the dark the first time. It is now my all-time favorite scary movie, and it's fairly recent.

I'm noticing a distinct lack of Terrifier and Terrifier 2 in these comments. Art the Clown is perhaps the best antagonist I've ever seen in the horror genre and true originality is rare in the modern horror filmscape.
The Ring is also good for originality as far as modern classics, though it's a whole book series in Japan.
Edit: I also liked The Shrine, forgot to mention that one. Again, originality.

Blood Quantum, for the humour and great cast. Outback, for being based in a true story.

I just recently watched Saltburn. Truly and genuinely disturbing. It's a psychological thriller. If you're not into that, well..
- Made me think of something that Brett Easton Ellis would write.
- I have a candle scent called Jacob Elordi's bath water

The Descent
The VVitch
The Shining
The Texas Chainsaw Massacre (1974)
Audition

"Ju-On: The Grudge" from 2002 was probably one of the scariest movies I've seen (if you don't mind reading subtitles). The US remake did not do it justice IMO. I don't know how well it holds up nowadays since it's so old and I was a lot younger when it came out.
- I also remembered it as insanely scary, but when I rewatched it recently it really didn't live up to my imagination. Maybe I had hyped it up too much in my head