Kat Richardson, born May 22, 1964, is an American writer recognized primarily for her Greywalker series of urban fantasy novels. Beyond this popular series, Richardson has contributed to various other forms of media and writing, including role-playing games, video games, and comic books. Her professional experience also extends to magazine writing, technical writing, and curriculum development and editing. She currently resides in Seattle, Washington, and is married. Richardson is also known for her advocacy for the legalization of ferrets in California.

The Greywalker series comprises nine novels, with Richardson indicating in the final installment that it would be the last for the foreseeable future. The protagonist, Harper Blaine, is a private investigator based in Seattle. Her life takes a supernatural turn when she is briefly killed while pursuing a case. After being medically revived, she discovers she possesses the ability to perceive supernatural beings like witches and vampires, see ghosts, and is aware of other elements of the hidden, mystical world. This near-death experience transforms her into a Greywalker, an individual capable of traversing the 'Grey'—a dimension existing between the physical world and the afterlife—at will.

Kat Richardson's most prominent contribution to literature is the Greywalker series, a collection of nine urban fantasy novels. The series centers on Harper Blaine, a Seattle-based private investigator whose life is irrevocably altered after a near-fatal experience. During a case, Blaine dies for a brief period before medical intervention brings her back. This event awakens within her supernatural abilities: she can identify witches and vampires, perceive ghosts, and recognize other aspects of the unseen world. This newfound awareness signifies her transformation into a 'Greywalker,' a term used to describe humans who can navigate the 'Grey,' a liminal space that exists between the material realm and the afterlife. This concept introduces a unique metaphysical dimension to the urban fantasy genre, exploring the boundaries between life, death, and the supernatural.

“This is the last Greywalker novel, at least for a while.”