Quicksilver Messenger Service was one of San Francisco's original psychedelic bands in the 1960s, formed around Dino Valenti. Valenti gathered together John Cipollina, Jim Murray, David Freiberg, Greg Elmore and Gary Duncan to create the group, which had to be put on hold almost immediately after its creation due to Valenti's imprisonment on drug charges.

In 1965, the band began a period of heavy touring on the West Coast of the United States, finally signing to Capitol Records in 1967 and released Quicksilver Messenger Service, followed by Happy Trails. By this time, Murray and Duncan had left, and Nicky Hopkins joined in time for 1970's Shady Grove; Duncan returned soon after. This line-up lasted for one year, followed by more personnel changes until the group finally disintegrated. The band reunited in 1975, and again in 1986.

Quicksilver Messenger Service was also the name of a London-based firm of motorcycle couriers in the 1990s, almost certainly inspired by the name of the band.