"Dear Mr. Fantasy" is a rock song by Traffic from their 1967 album, Mr. Fantasy. An extended live version (10:57) of the song also appears on the 1971 Traffic album Welcome to the Canteen. The lyrics were written by Jim Capaldi, while the music was written by Steve Winwood and Chris Wood.

The song has been covered by The Grateful Dead, Jimi Hendrix, Big Sugar and by Crosby, Stills, Nash and Young. Crosby, Stills, and Nash added two new verses to their version's lyrics:

Steve Winwood played an 8-minute and 13 second version on stage at Eric Clapton's 2007 Crossroads Guitar Festival and the song appears on the festival DVD.

The song was on the setlist of Steve Winwood and Eric Clapton's joint tour in 2009. A live recording appears on the album Live from Madison Square Garden.

As a solo act with a backing band, Dave Mason has performed the song live, himself covering duties of lead vocal, guitar and harmonica.

In addition the song was performed on multiple occasions throughout the 1980s by the Grateful Dead with keyboardist Brent Mydland on vocals. Phil Lesh and Friends, Gov't Mule and Widespread Panic occasionally cover the song. It also appeared on The Live Adventures of Mike Bloomfield and Al Kooper in 1969, where its chord progression morphed into "Hey Jude". This segue into "Hey Jude" also frequently appeared in the versions performed by the Grateful Dead and related bands.