盖·塞巴斯蒂安，Guy Theodore Sebastian AM is an Australian singer and songwriter who was the winner of the first Australian Idol in 2003, and a judge on Australia's The X Factor in 2010, 2011, 2012, 2015 and 2016. He represented Australia at the 2015 Eurovision Song Contest, finishing in 5th place. Sebastian is currently a coach on The Voice Australia as of 2019.