Tamsyn Muir (born 14 March 1985) is a New Zealand fantasy, science fiction, and horror author. Muir won the 2020 Locus Award for her first novel, Gideon the Ninth, and has been nominated for several other awards as well.

Muir was born March 14, 1985, in New South Wales, Australia. Her family moved to New Zealand when she was nine months old, so Muir grew up in Howick, New Zealand.^[1][2] In 2010, she earned a degree in education.^[1] She is also a 2010 graduate of the Clarion Workshop.^[3] She currently lives and works in Oxford, United Kingdom.^[4][5] Muir is a lesbian.^[6][7]

Muir's short story "The Deepwater Bride", published in The Magazine of Fantasy & Science Fiction in 2015, was nominated for the Nebula Award for Best Novelette,^[8] the World Fantasy Award—Short Fiction,^[9] the Eugie Award,^[10] and the Shirley Jackson Award for best novelette.^[11]

Gideon the Ninth, Muir's first novel and the first book of The Locked Tomb series, was published in 2019. It was awarded the 2020 Locus Award for Best First Novel and the 2020 Crawford Award, presented annually by the International Association for the Fantastic in the Arts. It was nominated for the Nebula Award for Best Novel and the Hugo Award for Best Novel. It finished third in the Goodreads Choice Awards for best science fiction in 2019.^[12]

Muir's fantasy novella Princess Floralinda and the Forty-Flight Tower was published in July 2020.^[13] It received a starred review from Publishers Weekly.^[14]

The second book in the Locked Tomb series, Harrow the Ninth, was published in August 2020,^[15] and was a finalist for the 2021 Hugo Award for Best Novel.^[16] It was followed by Nona the Ninth in 2022. The fourth instalment, Alecto the Ninth, was initially announced for release in 2023,^[17], but a cover and release date have not been revealed.

After the Locked Tomb books, Tor will be publishing Muir's cyberpunk western novella trilogy, beginning with Go Marching In.^[18]

In 2019, Amazon editors selected Gideon the Ninth as the best science fiction and fantasy book of the year.^[19]

In 2020, Amazon named Harrow the Ninth one of the best science fiction and fantasy novels of the year.^[20]

In 2022, Kirkus Reviews named Nona the Ninth one of the best science fiction and fantasy novels of the year.^[21] Audible named the audio recording as one of the best science fiction audiobooks of the year.^[22]