Super Junior , also known as simply SJ or SuJu , is a large thirteen member K-pop boy band formed by SM Entertainment in 2005. The group initially debuted with twelve members on November 6, 2005 with the single, "TWINS (Knock Out)". The initial twelve members, in age order (from oldest to youngest), are Leeteuk (the leader), Heechul, Han Geng, Yesung, Kang-In, Shindong, Sungmin, Eunhyuk, Donghae, Siwon, Ryeowook, and Kibum. The Chinese member, Han Geng, was chosen among the 3000 applicants through auditions held in China by SM Entertainment in 2001.

Many of the members had already pursued an entertainment career before Super Junior's debut through acting, VJ-ing, and modeling. On May 23, 2006 SM Entertainment announced the addition of a new member, Kyuhyun, making them the thirteen member group they are today.

News about SM Entertainment's unprecedented plans of forming a large twelve-member rotational group spread over the internet as early as 2004. The members chosen for the group became a popular topic of discussion within netizens after rumors spread that a handful of the members from the group had already made media appearances before. SM Entertainment gave their official announcement in forming a large twelve-member rotational band around early February 2005, the group being called Super Junior.