|Birth name||Karl Johan Schuster|
|Born||February 1, 1985|
|Occupations||Songwriter, record producer, musician|
|Associated acts||Max Martin, Dr. Luke|
Karl Johan Schuster (born February 1, 1985[source?]), better known by his stage name Shellback, is a songwriter, record producer and musician from Karlshamn, a small town in Southern Sweden. Together with Max Martin, he wrote "So What" and "Raise Your Glass" by Pink, "If U Seek Amy" and "3" by Britney Spears, "DJ Got Us Fallin' in Love" by Usher featuring Pitbull, and "Whataya Want from Me" by Adam Lambert. Also with Martin he co-wrote the Maroon 5 single One More Night.
- Hylse, Christian (2008-09-24). "Karlshamnskille toppar Billboardlistan" (in Swedish). BLT.se. Karlskrona, Sweden: BLT. Archived from the original on 2009-02-02. http://www.webcitation.org/query?url=http%3A%2F%2Fblt.se%2Fnoje_o_kultur%2Fkarlshamnskille-toppar-billboardlistan%28871740%29.gm&date=2009-02-01. Retrieved 2009-02-02.