A rock festival is an open-air rock concert featuring many different performers, typically spread over two or three days and having a campsite and other amenities and forms of entertainment provided at the venue. Some festivals are singular events, while others recur annually in the same location. Occasionally, a festival will focus on a particular genre, but many attempt to bring together a diverse lineup to showcase a broad array of popular music trends.

The KFRC Fantasy Fair and Magic Mountain Music Festival was an event held June 10 and 11, 1967, at the 4,000-seat Sidney B. Cushing Memorial Amphitheatre high on the south face of Mount Tamalpais in Marin County, California. Although 20,000 tickets were reported to have been sold for the event, as many as 40,000 people may have actually attended the two-day concert, which was the first of a series of San Francisco–area cultural events known as the Summer of Love. The Fantasy Fair was influenced by the popular Renaissance Pleasure Faire and became a prototype for large scale multi-act outdoor rock music events now known as rock festivals.