Games like The Mannequin Forest
Games like The Mannequin Forest include Escape the Backrooms, MiSide, Outlast, Buckshot Roulette, and Five Nights at Freddy's. We matched them by the tags players give The Mannequin Forest on Steam (Horror, Psychological Horror, Action, Jump Scare, and Indie): closest matches first, and among equally close ones the better-known games.

Escape the Backrooms
Shared: Horror · Psychological Horror · First-Person

MiSide
Shared: Psychological Horror · Horror · First-Person

Outlast
Shared: Horror · Psychological Horror · First-Person

Buckshot Roulette
Shared: Horror · First-Person · Indie

Five Nights at Freddy's
Shared: Horror · Psychological Horror · Indie

Poppy Playtime
Shared: Horror · Psychological Horror · Singleplayer

Garten of Banban
Shared: Horror · Psychological Horror · First-Person

Dark Deception
Shared: Horror · Psychological Horror · First-Person

Phasmophobia
Shared: Horror · Psychological Horror · First-Person

Five Nights at Freddy's: Security Breach
Shared: Horror · Singleplayer · First-Person

Outlast 2
Shared: Horror · Psychological Horror · First-Person

Resident Evil 7 Biohazard
Shared: Horror · First-Person · Psychological Horror

Resident Evil Village
Shared: Horror · Action · First-Person

IMSCARED
Shared: Horror · Psychological Horror · Indie

The Outlast Trials
Shared: Horror · Psychological Horror · First-Person

The Beast Inside
Shared: Horror · Action · First-Person

Five Nights at Freddy's 2
Shared: Horror · Psychological Horror · Singleplayer

No, I'm not a Human
Shared: Horror · Psychological Horror · Indie

Spooky's Jump Scare Mansion: HD Renovation
Shared: Horror · Indie · Action

Five Nights at Freddy's 3
Shared: Horror · Psychological Horror · Singleplayer

Ready or Not
Shared: Horror · Psychological Horror · Action

Lethal Company
Shared: Horror · First-Person · Psychological Horror

Gorilla Tag
Shared: Psychological Horror · Horror · First-Person

Slender: The Arrival
Shared: Horror · Indie · Psychological Horror