Matthew Arnold Thiessen (born August 12, 1980) is a Canadian-American musician, known for being co-founder, lead singer, guitarist, pianist, and primary songwriter for the Christian rock band, Relient K. He also works as a producer (beginning 2009), along with Mark Lee Townsend. He also dated Perry before she became famous for short amount of time.

Work with Katy Perry

He worked with Katy Perry on the following songs:

Songs from (A) Katy Perry (2005):

Songs from Teenage Dream: The Complete Confection (2012):