Games like Nightmare
Games like Nightmare include Outlast, Five Nights at Freddy's, Poppy Playtime, Outlast 2, and Five Nights at Freddy's 2. We matched them by the tags players give Nightmare on Steam (Horror, Singleplayer, Survival Horror, Psychological Horror, and Atmospheric): closest matches first, and among equally close ones the better-known games.

Outlast
Shared: Horror · Survival Horror · Psychological Horror

Five Nights at Freddy's
Shared: Horror · Singleplayer · Survival Horror

Poppy Playtime
Shared: Horror · Singleplayer · Survival Horror

Outlast 2
Shared: Horror · Survival Horror · Psychological Horror

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

Ultimate Custom Night
Shared: Horror · Singleplayer · Survival Horror

Resident Evil 7 Biohazard
Shared: Horror · Survival Horror · Singleplayer

Five Nights at Freddy's 4
Shared: Horror · Singleplayer · Survival Horror

Resident Evil Village
Shared: Horror · Survival Horror · Singleplayer

SOMA
Shared: Horror · Psychological Horror · Atmospheric

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

The Outlast Trials
Shared: Horror · Survival Horror · Psychological Horror

Slender: The Arrival
Shared: Horror · Survival Horror · Singleplayer

Five Nights at Freddy's: Sister Location
Shared: Horror · Singleplayer · Survival Horror

Garten of Banban
Shared: Horror · Singleplayer · Psychological Horror

Amnesia: The Bunker
Shared: Horror · Survival Horror · Atmospheric

Getting Over It with Bennett Foddy
Shared: Singleplayer · Psychological Horror · Horror

Amnesia: The Dark Descent
Shared: Horror · Survival Horror · Psychological Horror

Little Nightmares
Shared: Horror · Singleplayer · Atmospheric

FIVE NIGHTS AT FREDDY'S: HELP WANTED
Shared: Horror · Singleplayer · Survival Horror

Visage
Shared: Horror · Survival Horror · Psychological Horror

Lethal Company
Shared: Horror · Survival Horror · Psychological Horror

Alien: Isolation
Shared: Horror · Survival Horror · Atmospheric

Escape the Backrooms
Shared: Horror · Psychological Horror · Survival Horror