"Quicksilver Messenger Service" (sometimes credited as simply Quicksilver) is an American psychedelic rock band formed in 1965 in San Francisco. They were most famous for the single "Fresh Air", from the album Just for Love, which was their biggest hit, reaching No. 49 in 1970. Quicksilver Messenger Service gained wide popularity in the San Francisco Bay Area and through their recordings, with psychedelic rock enthusiasts around the globe, and several of their albums ranked in the Top 30 of the Billboard Pop charts. Though not as commercially successful as contemporaries Jefferson Airplane and The Grateful Dead, Quicksilver was integral to the beginnings of their genre.

With their jazz and classical influences and a strong folk background, the band attempted to create a sound that was individual and innovative. Member Dino Valenti drew heavily on musical influences he picked up during the folk revival of his formative musical years.

The style he developed from these sources is evident in Quicksilver Messenger Service's swung rhythms and twanging guitar sounds.