Classic rock (later known as dad rock) is a radio format that developed from the album-oriented rock (AOR) format in the early-mid 1980s. In the United States, it comprises rock music ranging generally from the mid-1960s to mid-1990s, primarily focusing on commercially successful blues rock and hard rock popularized in the 1970s–1980s AOR format. Classic rock's focus somewhat differs from the formats oldies (focusing on the more pop-oriented hits and earlier rock and roll of the 1950s–1970s) and classic hits (focusing on pop-oriented hits and pop rock of the 1970s–1990s).

The classic rock format became increasingly popular with the baby boomer demographic in the 1980s and 1990s. Although classic rock has mostly appealed to adult listeners, music associated with this format received more exposure with younger listeners with the presence of the Internet and digital downloading. Some classic rock stations also play a limited number of current releases which are stylistically consistent with the station's sound, or by legacy acts which are still active and producing new music.

Among academics and historians, classic rock has been discussed as an effort by critics, media, and music establishments to canonize rock music and commodify 1960s–1970s Western culture for audiences living in a post-baby boomer economy. The music selected for the format has been identified as predominantly commercially successful songs by white male acts from the Anglosphere, expressing values of Romanticism, self-aggrandizement, and politically undemanding ideologies. Classic rock has also been associated with rock's album era (1960s–2000s).

The classic rock format evolved from AOR radio stations that were attempting to appeal to an older audience by including familiar songs of the past with current hits. In 1980, AOR radio station M105 in Cleveland began billing itself as "Cleveland's Classic Rock", playing a mix of rock music from the mid-1960s to the present. Similarly, WMET called itself "Chicago's Classic Rock" in 1981. In 1982, radio consultant Lee Abrams developed the "Timeless Rock" format, which combined contemporary AOR with rock hits from the 1960s and 1970s.

KRBE, an AM station in Houston, was an early classic rock radio station. In 1983, program director Paul Christy designed a format which played only early album rock, from the 1960s and early 1970s, without current music or any titles from the pop or dance side of Top 40. Another AM station airing classic rock, beginning in 1983, was KRQX in Dallas-Fort Worth. KRQX was co-owned with an album rock station, 97.9 KZEW. Management saw the benefit in the FM station appealing to younger rock fans and the AM station appealing a bit older. The ratings of both stations could be added together to appeal to advertisers. Classic rock soon became the widely used descriptor for the format and became the commonly used term among the general public for early album rock music.

In the mid-1980s, the format's widespread proliferation came on the heels of Jacobs Media's (Fred Jacobs) success at WCXR, in Washington, D.C., and Edinborough Rand's (Gary Guthrie) success at WZLX in Boston. Between Guthrie and Jacobs, they converted more than 40 major market radio stations to their individual brand of classic rock over the next several years.

Billboard magazine's Kim Freeman posits that "while classic rock's origins can be traced back earlier, 1986 is generally cited as the year of its birth". By 1986, the success of the format resulted in older songs accounting for 60–80% of the music played on album rock stations. Although it began as a niche format spun off from AOR, by 2001 classic rock had surpassed album rock in market share nationally.

During the mid-1980s, the classic rock format was mainly tailored to the adult male demographic ages 25–34, which remained its largest demographic through the mid-1990s. As the format's audience aged, its demographics skewed toward older age groups. By 2006, the 35–44 age group was the format's largest audience; by 2014, the 45–54 year-old demographic was the largest.