Guy Theodore Sebastian (born 26 October 1981) is an Australian singer-songwriter and record producer. He was the first winner of Australian Idol in 2003, and was a judge on Australia's The X Factor between 2010 and 2012. Sebastian has released seven top ten albums including two number ones, which have all gained either platinum or multi-platinum certification. He has also achieved 12 top ten singles, including six number ones. Sebastian is the only Australian male artist in Australian chart history to achieve six number one singles, and places third overall for all Australian acts. Seven of his singles have been certified multi-platinum, including the 9× platinum "Battle Scars". His debut single "Angels Brought Me Here" was the highest selling song in Australia last decade. With 46 platinum and three gold certifications and combined album and single sales of over 3.3 million in Australia, he has the highest certifications and sales of any Australian Idol contestant.

Sebastian has also reached the top ten in New Zealand with an album and six singles, including two number ones, and gained six platinum and three gold certifications there. "Battle Scars", a collaboration with American rapper Lupe Fiasco, spent 20 weeks on the US Billboard Hot 100 chart, peaking at number 71 and achieved platinum certification. "Battle Scars" also reached number two in Norway. Sebastian has worked with other notable American musicians including Brian McKnight, Robin Thicke, Steve Cropper, John Mayer, Jordin Sparks and Eve.