Porter was born in Sydney. Her father was barrister Chester Porter and her mother, Jean, was a high school chemistry teacher. Porter attended the Queenwood School for Girls. She graduated from the University of Sydney in 1975 with a Bachelor of Arts majoring in English and History.
Porter's awards include The Age Book of the Year for poetry, the National Book Council Award for The Monkey's Mask and the FAW Christopher Brennan Award for poetry. Two of her verse novels were shortlisted for the Miles Franklin Award: What a Piece of Work in 2000 and Wild Surmise in 2003. In 2000, the film The Monkey's Mask was made of her verse novel of the same name. In 2005 her libretto, The Eternity Man, co-written with composer Jonathan Mills, was performed at the Sydney Festival.
Porter's most recent publication, her fifth verse novel, was El Dorado, about a serial child killer. The book was nominated for several awards including the inaugural Prime Minister's Literary Award in 2007 and for Best Fiction in the Ned Kelly Awards.
Since her death, The Bee Hut (2009) has been published posthumously, as has her final completed work, an essay on literary criticism and emotions and literature entitled On Passion.
Porter, who found many outlets for writing including fiction for young adults and libretti for chamber opera, was working on a rock opera called January with Tim Finn at the time of her death.
Porter was an open lesbian and in 1993 moved to Melbourne to be with her partner and fellow writer, Andrea Goldsmith. The couple were coincidentally both shortlisted in the 2003 Miles Franklin Award for literature. In 2009, Porter was posthumously recognised by the website Samesame.com.au as one of the most influential gay and lesbian Australians.
Porter was a self-described pagan, committed to pagan principles of courage, stoicism and commitment to the earth and beauty.
Porter had been suffering from breast cancer for four years before her death, but "many thought she was winning the battle," according to journalist Matt Buchanan. In the last three weeks of her life she became very sick and was admitted to hospital, where she was in intensive care for the final ten days. She died aged 54 on 10 December 2008.
On 21 February 2010, actress Cate Blanchett read excerpts from Porter's posthumously published short work on literary criticism and emotions in literature, On Passion at the Malthouse Theatre, Melbourne.
