Kate Forsyth completed a BA in Literature at Macquarie University and an MA in Writing at the University of Western Sydney, and a PhD at the University of Sydney. After completing her BA, she worked as a journalist while studying and writing.
Forsyth published her first novel in 1997: Dragonclaw, the first in the the six-part The Witches of Eileanan series.
Forsyth was president of the Poets' Union for two years and has had poetry (under the name Kate Humphrey) published in Australia, Denmark and the USA. These works were part of the new burgeoning of Australian fantasy in the 1990s, led by authors such as Sara Douglass. Forsyth followed this with a trilogy, Rhiannon's Ride, set in the same world. She has also published a number of fantasy series for younger readers, including Chain of Charms, Ben and Tim's Magical Misadventures, The Chronicles of Estelliana, and The Impossible Quest.
In 2012, Forsyth published the first of what would prove to be a series of revisionist fairytales, exploring the core of a number of well-known and well-loved fairy tales and fairy-tale creators through the transposition to other time periods and milieus. Bitter Greens, the first such novel, was Forsyth's rewriting of Rapunzel and formed part of her PhD dissertation: her PhD exegesis, exploring her long-term attraction to the Rapunzel story, was later published by FableCroft Publishing as The Rebirth of Rapunzel : A Mythic Biography of the Maiden in the Tower. Bitter Greens was followed by The Wild Girl (the origins of the Grimm household tales), The Beast's Garden (Beauty and the Beast variants in Nazi Germany), and Beauty in Thorns (Sleeping Beauty and the women of the Pre-Raphaelite movement).
Most recently, she published a collection of short stories set around a single well, The Silver Well, co-authored with Kim Wilkins: the collection won the 2017 Aurealis Award for Best Collection.
Forsyth's work has won numerous Aurealis Awards: she won both the Aurealis and the William Atheling Jr. Award for The Rebirth of Rapunzel, and was given an honourable mention at the 2013 Norma K. Hemming Awards for Bitter Greens.
In 2018, Forsyth and Sarah Mills launched Word of Mouth TV, a combination cooking and book-review show on YouTube. In June 2018, she announced a second collaboration with artist Lorena Carrington (with whom she produced Vasilisa the Wise and Other Tales of Brave Young Women), the forthcoming collection The Buried Moon and Other Tales of Brave Young Women.
Forsyth is the sister of Belinda Murrell. They are direct descendants of Charlotte Barton.