Nico and the Niners are elements from the conceptual world created by the American musical duo Twenty One Pilots, particularly featured in their song "Nico and the Niners" from the album Trench (2018). Nico is the head of the Nine Bishops who rule over a fictional place called Dema, symbolizing the negative forces or struggles in the mind of the band's lead singer Tyler Joseph. The Niners refer to the remaining eight bishops who, along with Nico, represent these oppressive forces. This imagery is a metaphor for Tyler's fears and anxieties. The Bishops of Dema are part of a storyline where Tyler (and others) want to escape their control, which relates to battling personal mental struggles and seeking freedom from oppression or internal turmoil.

The song "Nico and the Niners" itself is a reggae, rap, rock, and psychedelic musical piece tied to this narrative, with its music video depicting the resistance against these bishops by a group called the Banditos who seek to escape Dema.

In summary, Nico and the Niners are symbolic characters in the Twenty One Pilots universe, representing antagonistic, controlling forces that the protagonist tries to overcome.