First Night
Survive 1 night


Unlock this by surviving a night. I'd use a temporary shelter the first night since it's cheap on resources.

5 Star Hotel
Sleep on yacht


Unlock this by sleeping on the Yacht in the southern end of the map. I'd build my base around here, specifically on the peninsula to the left of it and unlock it whenever you find time to. Be careful of sharks in the water!

Be sure to grab Cassette Tape #1 as well.
The Yacht can be found on the blue star below.
Also, check out this map[theforestmap.com] as well to help you out!

Survivalist
Survive 5 nights


Unlock this by surviving the fifth night.

Bad Father
Survive 100 days
This is a hidden achievement.

Unlock this achievement by surviving 100 days in one save. Fun!

Fisherman
Catch fish with a trap. Alone in Single Player or together in Multiplayer.


Unlock this by catching a fish in an animal trap placed underwater. I'd place this in a pond somewhere where fish can be seen. I tried placing one on the coastline and got absolutely nothing for a while.

Monster
Kill a bunny. Alone in Single Player or together in Multiplayer.


Unlock this by killing a bunny in any way. According to the wiki, this achievement can only be completed in single player, though I'm fairly sure I completed it in multiplayer. Anyways, I'd build an animal trap in the forest somewhere and leave it unattended. Attacking them while running makes it much more annoying.

Unseen
Make and wear stealth armour


Unlock this by crafting stealth armor using one lizard skin and 15 leaves in your inventory and equipping it. Lizards can be found almost anywhere on the map. Try to hunt one before they notice you or they'll run away surprisingly fast. Crocodiles, which drop lizard skin (4x) as well, can be found in the northern end of the map by the river. Be careful of crocodiles though, as they are dangerous especially in early-game.

Birdseye
Kill bird with arrow


Unlock this achievement by killing any bird with an arrow. You can use either the crafted bow or the modern bow to obtain this. It's easier to wait until the bird is on the ground or perched to shoot.

Commercial Fisherman
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.


Unlock this achievement by killing six fish with one stick of dynamite. You'll have to find a spot on the coastline or in a river where six fish spawn and throw a dynamite next to them. Make sure to not throw it into the water or it'll be extinguished. I was able to do this in the pond near the main village.

Bite me!
Kill shark. Alone in Single Player or together in Multiplayer.


Unlock this achievement by killing a shark. A sticky bomb will stick to a shark and kill it. You can also use ranged weapons. Keep in mind that you can't attack sharks underwater and that they kill you in two-three bites. I used a bow to kill it with about three arrows. Don't waste your bombs.

Trophy Hunter
Kill all animal types and display heads


Unlock this by building head trophies for all animals in the game in one save. There are 11 animal heads required for this achievement.

1. Crocodile
   
2. Deer
   
3. Geese (found at exit of Cave 5)
   
4. Lizard
   
5. Boar
   
6. Raccoon (found in north)
   
7. Rabbit
   
8. Seagull
   
9. Shark (obtained from beached sharks)
   
10. Squirrel
    
11. Tortoise

Geese are the worst in this achievement. Geese can only be found in the eastern lake where Cave 5 (Submerged Cave) ends. You'll have to scare one to the shore by swimming near it and kill it and pick up the head before it goes underwater. They spawn during the day and can fly away when scared sometimes. I wouldn't blame you if you cheated on this one.

EDIT: Seems that you only require 11 different heads displayed in one game, not specific to any animal. This means that different types of Mutants will count towards this achievement as well! This will be way easier than getting a Goose and/or Raccoon. Thanks to hagen. for this info!

Splatter
Killed down enemy with rock


Unlock this by killing an enemy that is knocked over with a basic rock. Upgraded rocks do not count for this achievement. Since key-binds are difficult in this game, I'd just use a rock to deal 100% damage to make it easier for yourself.

Minor Cannibalism
Eat an enemy


Unlock this by eating two arms and two legs. Dried limbs do not count for this achievement. Cook them over a basic fire or fire pit and eat away.

Major Cannibalism
Eat an entire family


Unlock this achievement by eating 12 arms and 12 legs. Dried limbs do not count for this achievement as well. Cook them over a basic fire or fire pit and pretend everything's ok!

Choppy Chop
Chop up 50 bodies


Unlock this by chopping both of the arms and legs off 50 bodies. My friend unlocked this around our seventh day on multiplayer, so if you keep grinding you should unlock this soon.

Serial Killer
In Single Player, kill 100 cannibals


Unlock this achievement by killing 100 cannibals. Doesn't have to be in single player. Accumulates over different saves. I was able to earn it in multiplayer AND with my friend killing the last cannibal, so don't always trust achievement descriptions! You can kill enemies naturally in a longer game or set traps near a bonfire to lure cannibals into them. Have fun in court!

Handyman
Repair a shelter


Unlock this achievement by repairing a shelter. Build a hunting shelter, damage it without destroying it and use a Repair Tool (2x Stick, 1x Rock, 2x Cloth, 10x Sap) to repair it. This should unlock this for other players in a multiplayer session as well, weirdly enough.

Climate Change
Cut down 100 trees


Unlock this by cutting down 100 trees using axes, the chainsaw or explosives. I'm guessing you'll get this soon, just keep chopping away until you do. This achievement isn't too hard to get in Normal mode without cheats unlike the next one.

Don't Save The Forest
Cut down 1000 trees


Unlock this achievement by cutting down 1,000 trees using axes, the chainsaw or explosives. Have fun getting this one, I'm not excited!

You should be looking for Timmy
Build a gazebo
This is a hidden achievement.

Unlock this by finishing a gazebo blueprint. Treat yourself!

Longest Wall
Build a super long wall


Unlock this achievement by placing a blueprint for an inconveniently long wall. You only need to place a blueprint (ghost building) that uses about 250 logs total. This must be done with the Custom Wall, not the Defensive Wall.

Naturopath
Craft 10 medicine items


Unlock this achievement by crafting ten medicine items. The achievement only works with Herbal Medicine (1x Aloe + 1x Marigold) or Herbal Medicine+ (1x Aloe + 1x Marigold + 1x Coneflower), so you can craft five of each. These two items count towards the Crafty achievement. Aloe is super hard to find, so good luck.

Green Thumb
Grow all plant types


Unlock this achievement by growing all three plant types. Could be accumulative, but can't confirm. You must build a garden plot first and then harvest blueberries, aloe and coneflowers around the island. Once you've obtained the seeds, plant them by pressing the key-bind shown in the middle of the plot.

You are a fun guy
Eat all mushroom types


Unlock this achievement by eating all 6 mushroom types found in The Forest.


This one was annoying but not difficult. You can stare at a mushroom for around 5 seconds to discover it and utilize that to prevent backtracking.

The achievements listed below are linked to the story or can only be achieved by going into story-related areas.

Difficulty doesn't matter for these achievements. I was able to earn all of these in Peaceful mode. In Peaceful mode, you will still have to fight the Boss Mutant.

Make It Rain
Set off the sprinklers in end game
This is a hidden achievement.

Unlock this achievement by turning on the sprinklers in certain hallways in the Lab. You can shoot an enemy with a fire arrow/flare gun or you can shoot the sprinkler directly. In peaceful mode, you must shoot the sprinkler directly.

Daily Grind
Drink from coffee machine
This is a hidden achievement.

Unlock this achievement by drinking coffee from the coffee machine. This coffee machine can be found in the Sahara Laboratory cafeteria. There's also one right before the Boss Mutant's room.

Big Spender
Buy a soda and candy from vending machine
This is a hidden achievement.

Unlock this achievement by buying a Soda and Snack from two vending machines. These vending machines can be found in the Sahara Laboratory cafeteria as well. These are also found in the hallway before the Boss Mutant. Treat yourself!

Gross!
Drink from the water cooler that has the human head inside it
This is a hidden achievement.

Unlock this achievement by interacting with the cooler with a head inside the tank. This water cooler can be found in the Sahara Laboratory, past the second access door and up the rock cave after you take out the Boss Mutant. It'll be in an office on the right with an active projector.

If you're confused, I'd check every room you can after taking out the boss.

Survive The Forest
Finish Game


Unlock this achievement by beating the game. Get ready for the sequel.

Cave 1 has two items and one passenger that count towards achievements.

• Get Closure - Cave 1 has one passenger. (1A)
  
• Gabe Fan - Cave 1 has Cassette Tape #5.
  
• Good Father - Cave 1 has Timmy's Toy Torso.

Cave 1 also includes a Katana, Flashlight and Photo Cache #9.

Cave 2 has two items that count towards achievements.

• Gabe Fan - Cave 2 has Cassette Tape #4.
  
• Good Father - Cave 2 has Timmy's Toy Head.

Cave 2 also includes a Modern Axe, Compass and a Map.

Equip the compass after obtaining it.

Boy Scout
Use the compass


Unlock this achievement by equipping the compass. Pretty self-explanatory.

Cave 3 has one item that count towards achievements.

• Good Father - Cave 3 has Timmy's Toy Left Arm.

Cave 3 also includes a Chainsaw, Old Gun Ammo and Photo Cache #1.

Cave 4 has one item that count towards achievements.

• Gabe Fan - Cave 4 has Cassette Tape #2.

Cave 5 has one item that counts towards achievements.

• Good Father - Cave 4 has Timmy's Toy Left Leg.

Cave 5 also includes a Rebreather, Flashlight, Rusty Axe and Photo Cache #3.

Cave 6 (technically) has one item that counts towards achievements.

• Survive The Forest - Cave 6 has a Keycard which is important to the story.

Cave 6 also includes a Camcorder and Camcorder Tape #1 and #2.

Cave 7 has three items and seven passengers that counts towards achievements.

• Get Closure - Cave 7 has seven passengers. (11E, 11D, 5B, 11A, 4B, 10A, 3C)
  
• Good Father - Cave 7 has Timmy's Toy Right Leg and Toy Right Arm.
  
• Step Master - Cave 7 has the Pedometer.

Cave 7 also includes a Modern Bow, Tennis Racket, Flashlight, Old Gun Ammo, Photo Cache #4 and #5 and Camcorder Tape #4.

After getting the last few toy parts, go into your inventory and combine all six to create the Full Toy.

Good Father
Collect all robot pieces


Unlock this by crafting the Full Toy. These parts are scattered around Caves 1, 2, 3, 5 and 7.

Cave 8 has no items but visiting it still counts towards the Spelunker achievement.

Cave 9 has no items linked to achievements but like stated before; it's still important to visit it.
Cave 9 does have a Climbing Axe, which will be important for Cave 7.

Cave 10 has one item that counts towards achievements.

• Gabe Fan - Cave 10 has Cassette Tape #3.

Gabe Fan
Collect all cassette tapes!


Unlock this by collecting all cassette tapes. After collecting #3 from Cave 10, this achievement should be finished. If it isn't, make sure to check the Yacht to make sure you collected Cassette Tape #1.

Spelunker
Explore all caves


Unlock this by exploring all the caves (not sure to completion). You should unlock this after exploring Cave 10, but it's smart to get the Map from Cave 2 first to avoid any backtracking.

Cave HC has no items but is important to the story.

There are more caves in the game but these are all I found that seem to be important to achievements.

Pacifist
In Single Player, Don't kill any cannibals for more than 10 days in a row


Unlock this achievement by not killing cannibals for ten days. Doesn't have to be in single player. Could be accumulative, but can't confirm.

Get Closure
Find all missing passengers


Unlock this by finding all the missing passengers from the plane. See Passengers[theforest.fandom.com] from the wiki or use this map[theforestmap.com]. (Sorry to be lazy, I just think this would be easier to follow.)

Step Master
Pass 50,000 steps


Unlock this by using the Pedometer found in Cave 7 and passing 50,000 steps. Keep in mind steps aren't counted until you have the Pedometer.

Crafty
Craft all items


Unlock this by crafting at least 26 of the items listed below.

Demolition Man
Set off 20 bombs


Unlock this by setting off 20 bombs. Dynamite, sticky bombs and head bombs seem to work for this achievement.

Demolition Expert
Knock down 6 or more trees with 1 explosive


Unlock this by using an explosive to knock down six trees. Find a large clump trees, throw some dynamite and watch them fall.

Vegan
Play through entire game without killing or eating animals. Alone in Single Player or together in Multiplayer.


Unlock this by finishing the game without killing animals. Assuming killing one animal will end the run, it's better to beat the game as quickly as possible. This doesn't apply to cannibals. You'll need only the Rebreather (in Cave 5), Climbing Axe (in Cave 9), and Keycard (in Cave 6) to finish the game. To obtain the achievement, you'll need to save Timmy.

This achievement will be unlocked after Timmy's cutscene, so don't worry if you don't get it with Survive The Forest.

Be Nice
Share a food or drink item in MP


Unlock this achievement by combining your metal tin tray with any food or drink item, equipping it and having another player collect it. A metal tin tray can be found in the back of the plane and food and drink items can be found scattered around the wreckage. Should be easy to do immediately.

Camp Out
Sleep with another player (group sleep)


Unlock this achievement by sleeping in the same shelter with another player. Great wording!

First Responder
Revive one co-op player


Unlock this achievement by reviving a player before they die.

Be Extremely Nice
Share a weapon in MP


Unlock this achievement by combining the metal tin tray with a weapon, equipping it and having another player collect it. I did this with a weak spear (two sticks) and got it.

Medic
Revive 10 co-op players


Unlock this achievement by reviving ten players before they die.