Characters of Undertale and Deltarune

A screenshot from the 'True Pacifist' ending of Undertale, featuring friends the player makes along the way. From left to right: Toriel, Sans, Papyrus, Frisk, Undyne, Alphys, and Asgore.

The fantasy role-playing video game Undertale, developed by Toby Fox, takes place in a universe where monsters once coexisted with humans, but have long since been forgotten in modern times. Its main character is a human child who falls into the Underground, a large cave below Mount Ebott where human wizards trapped the monsters following an ancient war and from which they seek to escape. Its spiritual sequel, Deltarune, is an anagram of Undertale, and takes place in a parallel universe featuring many of the same characters. In Deltarune's universe, humans and monsters still coexist in the modern day. The main character, Kris, discovers the Dark World, an alternate realm inhabited by Darkners, which are beings brought to life from objects originally from the Light World (the regular world). They embark on a quest to close the Dark Fountains before darkness overtakes the real world.

The following is a list of major characters who appear in one or both games in the series. The characters of both games were well received by critics and fans for their humor and in-depth characterization shown through different moral choices. Some characters gained notoriety for their ability to break the fourth wall, manipulating gameplay elements normally only accessible to the player, such as saving.