Born in Sydney, Australia, Courtney and his sister were raised in Sydney's leafy northwest suburbs, attending Galston Public School where their mother, Karen, was a teacher. His father, Chris, was a civil servant with the state electricity company, implying that there were no show business influences in the family when Jai caught the acting bug as a 10-year-old. He went on to develop his dramatic skills at Cherrybrook Technology High School. At 18, Courtney, like many of Australia's finest thespians before him, tried and failed to win a place at the country's leading acting school, the National Academy for Dramatic Art (NIDA). However, he later nabbed a spot at the respected Western Australian Academy of Performing Arts (WAAPA), Hugh Jackman's alma mater. WAAPA trains students in everything from classic theater roles to screen musicals, a diversity Courtney set about exploring after graduation.Four head-turning appearances in TV melodramas "All Saints" (Seven Network, 2008-09) and "Packed to the Rafters" (Seven Network, 2008-2013) brought him to the attention of the Australian public. Until the 2010s, however, his girlfriend, WAAPA-trained Gemma Pranita, was the better-known face courtesy of her starring on the popular soap opera "Neighbours" (Eleven, 1985-). Courtney also featured on the big screen in 2009 in the Australian road movie "Stone Bros." The limited work didn't make him a star in Australia, but was enough to give him the chance to secure the part of Varro in the series "Spartacus: Blood and Sand" (Starz, 2010). The historical drama, starring Welsh-Australian Andy Whitfield, was a cable hit in the United States. Courtney left the series behind to concentrate on breaking into film when close friend Whitfield died in 2011 from non-Hodgkin lymphoma.With a leg up in Hollywood, the actor regularly headed to Los Angeles to audition. In mid 2011, "Jack Reacher" star and producer Tom Cruise was impressed by Courtney's audition tape and immediately cast him. The role funded Courtney's continued "commute" from Sydney to LAX, but offers of quality work were coming from home rather than abroad, so in 2012 he was on the verge of setting aside his Hollywood dream. However, while preparing to fly to Sydney, Courtney's agent called, advising him to drop everything to read with Bruce Willis for a shot at the career-changing role of the legend's son in the fifth film in the of the "Die Hard" franchise. After co-starring in Joel Edgerton's thriller "Felony" (2013) and fantasy "I, Frankenstein" (2013), Courtney focused his attention on the American market in earnest, co-starring in TA chase thriller "Divergent" (2014) and its sequel "The Divergent Series: Insurgent" (2015), as well as a key supporting role in Angelina Jolie's World War II POW drama "Unbroken" (2014). After co-starring in franchise reboot "Terminator Genisys" (2015) and post-apocalyptic thriller "Man Down" (2015), Courtney landed a major supporting role in the blockbuster "Suicide Squad" (2016) playing DC Comics supervillain Boomerang opposite Will Smith, Margot Robbie and Viola Davis.