Byrne was born in Sydney, Australia, the daughter of Jane, a primary school administrator, and Robin Byrne, a semi-retired statistician and market researcher. She attended Balmain Public School and Hunters Hill High School before attending Bradfield Senior College in North Sydney. She has an older brother, George, and two older sisters, Alice and Lucy. She began taking acting classes at age eight, Read more...

Byrne was cast in her first film role, Dallas Doll, when she was 12 years old. She has appeared in a variety of Australian television shows including Heartbreak High, Echo Point, and the film Two Hands alongside Heath Ledger. She appeared in The Date, My Mother Frank, and Clara Law's The Goddess of 1967 for which she obtained the Female Volpi Cup at the 2000 Venice Film Festival. Meanwhile, she Read more...

Byrne has been in a relationship with Australian writer, director and actor Brendan Cowell for over four years. The couple have maintained a long-distance for much of their relationship, with work commitments meaning they were often on separate continents.

However, Cowell has planned a move from Sydney to New York City, due to Byrne's success on Damages. Previously she dated Australian writer, Read more...