* Flowey
* Flowey is the first major character that the protagonist encounters in Undertale, serving as the main antagonist for the majority of the game, specifically the Neutral and True Pacifist routes.
* He provides an introduction to the mechanics of encounters by sharing "friendliness pellets," which are actually harmful bullets. His main philosophy is "KILL or BE KILLED."
* Abilities
* Five-bullet spread
* Large ring of bullets
* Speeds up

* Toriel
* Toriel is the second major character the protagonist encounters in Undertale.
* She saves the protagonist from Flowey and guides them through the Ruins.
* Abilities
* Paw sweep
* Fire waves
* Fire helix
* Faltering

* Sans
* Sans is the brother of Papyrus and a major character in Undertale.
* He serves as a supporting character in a Neutral and True Pacifist Route and as the final boss and heroic antagonist in a Genocide Route.
* Abilities
* Teleport/"shortcuts."
* Gaster Blasters
* Karmic Retribution
* Blue mode
* Light ble attack
* Attacking the protagonist in the selection menus

* Papyrus
* Papyrus is the brother of Sans and a major character in Undertale.
* His main motive is to capture a human so he can become a member of the Royal Guard.
* Abilities
* Blue attack

* Undyne
* Undyne is a weapon-based opponent, wielding a spear to change the protagonist's SOUL mode while using multiple spear patterns and combinations to attack.
* Abilities
* Green mode
* Arrows
* Spears

* Alphys
* Dr.Alphys is a female, reptilian monster that lives in the lab in western Hotland.
* She is the incumbent Royal Scientist, a position she was awarded by Asgore after the death of her predecessor. Asgore hired Alphys because she told him that she had created a SOUL; in reality, she created a robotic body for a ghost.
* Abilities
* None?

* Mettaton
* Mettaton is a robot with a SOUL and was built by Alphys.
* Initially poised as an entertainment robot turned human killing robot, Mettaton is later revealed to have only acted as such.
* Mettaton is the sole television star of the Underground.
* Abilities
* Yellow mode
* Lasers
* Bombs
* Extendable arms
* Mini Mettaton's
* Legs

* Asgore
* King Asgore Dreemurr is the ruler of the Underground and its denizens, monsters.
* He is the ex-husband of Toriel, father of Asriel Dreemurr, adoptive father of the first human, and the penultimate boss of the Neutral Route.
* While not necessarily evil or malicious, he serves as one of the main antagonists, scheming to kill seven humans and use their SOULs to break the barrier which traps the monsters in the Underground.
* Abilities
* Light blue attacks
* Orange attacks
* Trident
* Fireballs

* Asriel
* Asriel Dreemurr is the biological child of Toriel and Asgore and the adoptive brother of the first human.
* He serves as the final boss of a True Pacifist Route.
* Abilities
* Fire magic
* Star Blazing
* Shocker Breaker
* Chaos Saber
* Chaos Buster
* Hyper Goner
* Angel of Death

* Frisk
* Frisk is the playable character and main protagonist of Undertale.
* After Frisk falls into the Underground, they embark on a journey to return to the surface.
* Frisk is the last of the eight humans to fall into the Underground after travelling to Mt. Ebott.
* Frisk is not the "fallen human" named at the beginning of the game.
* Abilities
* Time travel
* Time manipulation
* Timeline creation and destruction
* Reality manipulation

* Chara
* Chara also known as the first human or the fallen human, is the first human to fall into the Underground.
* Chara is also the human that the player names at the start of the game, and not the controllable character who is played throughout the entirety of Undertale.
* Abilities
* Body possession
* Timeline creation and destruction
* Time and reality manipulation