A goblin is a small, grotesque, and often mischievous or malevolent creature that appears in the folklore of multiple European cultures. The term "goblin" is more generic for those small creatures that live in dark places and cause trouble, but in more recent years, the term has become more concentrated on green-creatures that live in caves and terrorize children. Some accounts claim that goblins are mostly invisible to the human eye, and thus act as phantoms. However, even in traditions where they are invisible, it is still widely known what they look like underneath their invisibility. Goblins are often associated with other diminutive spirits such as fairies, demons, brownies, dwarfs, duendes, gnomes, imps, and kobolds.

In modern fiction, goblins are often portrayed as evil creatures that live in the mountains or underground. In J. R. R. Tolkiens The Hobbit, the evil creatures living in the Misty Mountains are referred to as goblins. In The Lord of the Rings, the same creatures are primarily referred to as orcs. Goblinoids are a category of humanoid legendary creatures related to the goblin. The term was popularized in the Dungeons & Dragons fantasy role-playing game, in which goblins and related creatures are a staple of random encounters. Goblinoids are typically barbaric foes of the various human and "demi-human" races.

In recent years, the term "goblin mode" has been used to describe a response to the anxieties of the pandemic and the challenges of the return to so-called "normality." It is also about challenging the essentially unattainable ideals expressed on social media. "Goblin mode" expresses a desire to do things that are considered socially unacceptable, such as grocery shopping in your pyjamas or talking on your phone while on the toilet.