Ryan Kwanten was born in Sydney, New South Wales to Eddie Kwanten, a worker at NSW Maritime, and Kris, a lifeline op-shop coordinator. He is of Dutch ancestry on his father's side. Ryan has two brothers, Mitchell, who is a musician and Lloyd, who is a doctor. He attended Catholic school. Ryan began acting on the TV shows A Country Practice, Hey Dad..! and Spellbinder. In 1997, he joined the cast of the Australian soap opera Home and Away, playing lifeguard Vinnie Patterson.
He eventually chose to leave the series in 2002, shortly after his character married and became a father. Moving to the United States, Ryan was cast as Jay Robertson in the Lori Loughlin-starring series Summerland, which ran from 2004 to 2005. He appeared in the films Flicka, with Maria Bello, Alison Lohman and Tim McGraw, and Dead Silence, a horror movie in which he played the leading role.
Ryan made an appearance in a Law and Order: SVU episode that aired on 2 December 2008, in which he portrayed US Marine Corps Master Sergeant Dominic Pruitt who was (falsely) accused of raping and murdering a fellow Marine who was pregnant.
In 2009, he starred in the film Don't Fade Away with Mischa Barton and Beau Bridges.
Kwanten currently plays the role of Jason Stackhouse in True Blood, an HBO television series based on Charlaine Harris' Southern Vampire Mysteries.