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. With Relient K, he has released six full-length albums, including three that were certified Gold, and three that peaked in the top twenty on the Billboard 200. Outside of his work with Relient K, Thiessen maintains a low-profile side project called MatthewThiessen and the Earthquakes. In 2009, he co-produced and collaborated on Owl City's album Ocean Eyes. He co-manages an imprint of Gotee, Mono Vs Stereo, along with Matt Hoopes. He has done guest vocals for Deas Vail, John Reuben, Owl City, The Fold, and Run Kid Run, to name a few. He also works as a producer, along with Mark Lee Townsend.