Claes Olof af Geijerstam (Swedish pronunciation: [ˈklɑːs ɑːv ˈjɛ̂jːɛˌʂʈam]; born 6 February 1946), nicknamed Clabbe (IPA: [ˈklâbːɛ]), is a Swedish musician, radio personality and DJ who is mostly famous for his talent of rapid speech and his many years as a radio DJ.

He is also known for his role as jury member on the popular Swedish version of Pop Idol during 2004–2006.

They competed in Melodifestivalen 1973 with the song "Sommar'n som aldrig säger nej."

As a result of that victory, the duo represented Sweden in the Eurovision Song Contest 1973, where they translated their song into English with the title "You're Summer (You Never Tell Me No)" and finished fifth.

In 1979, af Geijerstam was the sound engineer for ABBA's North American and European tour.