Garth Richard Nix (born 19 July 1963) is an Australian writer who specializes in children's and young adult fantasy novels, notably the Old Kingdom, Seventh Tower and Keys to the Kingdom series. He has frequently been asked if his name is a pseudonym, to which he has responded, "I guess people ask me because it sounds like the perfect name for a writer of fantasy. However, it is my real name."

Garth Nix was born in 1963 in Melbourne, Australia, to the sound of the Salvation Army band outside playing 'Hail the Conquering Hero Comes' or possibly 'Roll Out the Barrel'. Garth left Melbourne at an early age for Canberra (the federal capital) and stayed there till he was nineteen, when he left to drive around the UK in a beat-up Austin with a boot full of books and a Silver-Reed typewriter. Despite a wheel literally falling off the Austin, Garth survived to return to Australia and study at the University of Canberra. After finishing his degree in 1986, he worked in a bookshop, then as a book publicist, a publisher's sales representative, and editor. Along the way, he was also a part-time soldier in the Australian Army Reserve, serving in various capacities.

Garth Nix has been a full-time writer since 2001, but has also worked as a literary agent, marketing consultant, book editor, book publicist, book sales representative, bookseller, and as a part-time soldier in the Australian Army Reserve.

Garth’s books include the Old Kingdom fantasy series: Sabriel, Lirael, Abhorsen, Clariel, Goldenhand and Terciel and Elinor; SF novels Shade’s Children and A Confusion of Princes; fantasy novels Angel Mage and The Left-Handed Booksellers of London; and a Regency romance with magic, Newt’s Emerald. His novels for children include The Ragwitch; the six books of The Seventh Tower sequence; The Keys to the Kingdom series and Frogkisser! His short fiction includes more than 60 published stories, some of them collected in Across the Wall and To Hold the Bridge.

He has co-written several books with Sean Williams, including the Troubletwisters series; Spirit Animals Book Three: Blood Ties; Have Sword, Will Travel; and Let Sleeping Dragons Lie.

More than six million copies of Garth’s books have been sold around the world, they have appeared on the bestseller lists of The New York Times, Publishers Weekly, The Bookseller and others, and his work has been translated into 42 languages. He has won multiple Aurealis Awards, the Ditmar Award, the Mythopoeic Award, CBCA Honour Book, and has been shortlisted for the Locus Awards, the Shirley Jackson Award and others.