Gerdur Kristný was born on June 10, 1970, and brought up in Reykjavík. She graduated in French and comparative literature from the University of Iceland in 1992. Her BA dissertation was on Baudelaire's Les fleurs du mal. After a course in media studies at the University of Iceland from 1992-1993 she trained at Denmark's Radio TV. She was editor of the magazine Mannlíf from 1998 to 2004, but is now a full-time writer.
Gerður Kristný has published poetry, short stories, novels, and books for children, as well as a book about the Westman Islands Festival in 2002 and the biography Myndin af pabba—saga Thelmu (A Portrait of Dad—Thelma's Story). This true story of Thelma and her sisters growing up in the ’60s and ’70s with their sexually abusive father shocked readers in Iceland and Gerður received The Icelandic Journalism Award in 2005 for the book.
Other awards for her work include the Children's Choice Book Prize in 2003 for her book Marta Smarta (Smart Marta), the Halldór Laxness Literary Award in 2004 for her novel Bátur með segli og allt (A Boat With a Sail and All) and the West-Nordic Children's Literature Prize in 2010 for the novel Garðurinn (The Garden). Gerður's collection of poetry, Höggstaður (Soft Spot), was nominated for the Icelandic Literature Prize in 2007 and she then won the prize in 2010 for her poetry book Blóðhófnir, which is based on the myth about Freyr and the poet's namesake Gerður Gymisdóttir from the Eddic poem Skírnimál.
Gerður Kristný's poetry and short stories have been included in school textbooks at the elementary and secondary level, as well as in anthologies and periodicals published in Iceland and abroad. The biography Myndin af pabba was published in Sweden in 2008 as Bilden av pabba.
Gerdur Kristný lives in Reykjavík with her husband and two sons.