Gunnar Madsen is an American composer and vocalist. He was the founder and leader of The Bobs before leaving the group in 1991, and has released several albums as a solo artist since then. Madsen learned to play guitar as a teenager and studied classical piano at UC Berkeley. He worked for a singing telegram corporation before founding the a cappella ensemble The Bobs in 1981. Among other successes, Madsen was nominated for a Grammy award for their arrangement of "Helter Skelter" by The Beatles.

Madsen left The Bobs in 1991 and began writing video game music for the Atari system. He began releasing albums as a solo artist in 1997 and has released seven as of 2009. His efforts include three children's records (all recipients of Parents' Choice Gold Awards), and three recordings of instrumental compositions.

The title song from his CD Old Mr. Mackle Hackle was adapted by Madsen into a children's book for Little, Brown & Co. He provided the singing voice for Don Cheadle's portrayal of Sammy Davis, Jr. in the HBO film The Rat Pack, and arranged music for and appeared in the 2006 Vince Vaughn/Jennifer Aniston film The Break-Up. His music has also been featured in HBO's Sex and the City and the films Breaking the Rules and Just a Kiss. A musical based on the life story of The Shaggs (co-written with Joy Gregory) is scheduled for production at Playwrights Horizons in their 2010-2011 season.