Games like Species: Unknown
Games like Species: Unknown include Lethal Company, Escape the Backrooms, Nuclear Nightmare, Backrooms: Escape Together, and Dead by Daylight. We matched them by the tags players give Species: Unknown on Steam (Horror, Online Co-Op, First-Person, Atmospheric, and Aliens): closest matches first, and among equally close ones the better-known games.

Lethal Company
Shared: Horror · Online Co-Op · First-Person

Escape the Backrooms
Shared: Horror · Online Co-Op · First-Person

Nuclear Nightmare
Shared: Online Co-Op · Horror · First-Person

Backrooms: Escape Together
Shared: Horror · Online Co-Op · Multiplayer

Dead by Daylight
Shared: Horror · Online Co-Op · Survival Horror

Inside the Backrooms
Shared: Horror · Survival Horror · Online Co-Op

Alien: Isolation
Shared: Horror · Survival Horror · Atmospheric

Pacify
Shared: Horror · Online Co-Op · First-Person

R.E.P.O.
Shared: Horror · Online Co-Op · First-Person

Dying Light
Shared: Horror · Online Co-Op · Survival Horror

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

GTFO
Shared: Horror · Online Co-Op · Survival Horror

Phasmophobia
Shared: Horror · Online Co-Op · First-Person

Outlast
Shared: Horror · First-Person · Atmospheric

Content Warning
Shared: Horror · Online Co-Op · Exploration

BIGFOOT
Shared: Horror · Online Co-Op · Survival Horror

PANICORE
Shared: Horror · Online Co-Op · Survival Horror

Left 4 Dead 2
Shared: Online Co-Op · Horror · Multiplayer

PEAK
Shared: Online Co-Op · Multiplayer · First-Person

DEVOUR
Shared: Horror · Online Co-Op · Survival Horror

Aliens vs. Predator™
Shared: Horror · Aliens · Multiplayer

Subnautica 2
Shared: Horror · Multiplayer · Exploration

Starship Troopers: Extermination
Shared: Online Co-Op · First-Person · Aliens

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