Q Hayashida, born in Tokyo in 1977, is the pen name of a Japanese manga artist known for a distinctive visual style that blends horror, comedy, and intricate detail. The creator maintains a high level of privacy, with her real name and face not publicly known. Before beginning her career in manga, she studied oil painting at the Tokyo University of the Arts, a background that has significantly influenced her artistic approach and attention to texture. Her professional debut came in 1997 when she earned second place in Monthly Afternoon's seasonal award competition for a one-shot titled Sofa-chan, a story about a female ghost living in a couch.

Following her debut, Hayashida wrote and illustrated Maken X Another, an adaptation of the 1999 video game Maken X, which was published in Monthly Magazine Z from 1999 to 2001. She is best known as the original creator of the manga series Dorohedoro. The series was serialized from 2000 to 2018, beginning in Monthly Ikki and later moving to Hibana and then Monthly Shōnen Sunday following the closures of its previous publications. The complete series spans 23 volumes. Dorohedoro received a television anime adaptation that first aired in 2020, produced by the animation studio MAPPA. A second season of the anime is scheduled to premiere in April 2026.

After concluding Dorohedoro, Hayashida launched a new manga series titled Dai Dark in Monthly Shōnen Sunday in March 2019. As of October 2024, eight compiled volumes of the ongoing series have been released. The story follows a teenage alien named Zaha Sanko, whose bones are rumored to grant any wish, forcing him to constantly fend off attacks while searching for the source of the curse. The manga is licensed for English release in North America by Seven Seas Entertainment.

Throughout her body of work, Hayashida is recognized for balancing elements of horror and comedy. Her stories often feature dark, grotesque imagery and worlds with gritty atmospheres, yet they are populated with characters who possess an endearing and often humorous quality. This blend of violence and absurdity is a signature aspect of her narrative identity. Her background in oil painting is evident in her detailed artwork, and she is known to use a variety of artistic tools and media, including paint and textiles, particularly for her color illustrations and volume covers. A traveling exhibition of her original artwork, spanning 20 years of her career, was held in Tokyo and featured over 400 pieces, including mixed media works and original manuscripts. Her industry significance is marked by the long-running success of her series, the dedicated fanbase for her unique aesthetic, and the continued adaptation of her work into other media, cementing her status as a distinctive and influential voice in manga.