Garth Nix was born in Melbourne in 1963 and moved to Canberra soon thereafter. After leaving school, Nix joined the Army Reserve and enjoyed being a part-time soldier for the next five years. On a trip to England and Europe, Nix wrote a few stories, one of which, 'Sam, Cars and Cuckoo', became his first published short story in 1984.
While working in a book shop in Canberra, Nix began writing his first novel, The Ragwitch, which was published in 1990 in Australia and in 1994 in the US. He graduated with a degree in professional writing from the University of Canberra in 1996. Nix worked for several years in the publishing business in Sydney before travelling extensively including taking the overland route from London to Pakistan, tracing the footsteps of Alexander the Great. During that journey, Nix wrote part of his next book Sabriel, a fantasy novel for young adults, about a magical girl from a very different world, which won several awards and was short-listed for six US State awards. He managed to work and write part-time for several years before becoming a full-time writer at the end of 2001.
Nix's followed Sabriel with the standalone novel Shade's Children (1997) before returning to the Old Kingdom with a follow-up to Sabriel: Lirael: Daughter of the Clayr (2001), which won the 2002 Adelaide Festival Award for Children's Literature. The third in the series, Abhorsen, was published in 2003. Clariel followed in 2014 and the final novel, Goldenhand, in 2016. The Old Kingdom series (including collections of short stories) has won national and international awards including the Aurealis Award (four times), the American Library Association Honor Book listings (twice), and the Ditmar Award: Goldenhand was nominated for both the Carnegie Medal and a Locus Award.
Standalone novels for young adults include A Confusion of Princes, Newt's Emerald, and Frogkisser!: the latter, illustrated by Kathleen Jennings, brought Nix a second nomination for a Carnegie Medal.
His works for younger readers include Serena and the Sea Serpent (2000) and the six-book sequence The Seventh Tower (2000). More recently, he has collaborated with Sean Williams on the series Troubletwisters and Have Sword, Will Travel. His short stories, which he began in 1984, also regularly attract award nominations: he won the Aurealis Award for Best Short Fantasy Story in 2007 with 'Sir Hereward and Mister Fitz Go to War Again'.