Classic rock is a radio format which developed from the album-oriented rock (AOR) format in the early 1980s. In the United States, the classic rock format features music ranging from the late 1960s to the late 1980s, primarily focusing on the hard rock genre that peaked in popularity in the 1970s. Classic rock stations re-create, in part, the sound of album-oriented rock stations of the 1970s and 1980s (although usually with a much more limited playlist) and appeal mainly to adults, rather than teenagers (despite this, many classic rock acts consistently attract new generations of fans). Some classic rock stations also play a limited number of current releases which are stylistically consistent with the station's sound, or from established classic rock artists that are still producing new albums.

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 1982, radio consultant Lee Abrams developed the Timeless Rock format which combined contemporary AOR with hits from the 1960s and 1970s.[3] By 1986, the success of the format resulted in oldies accounting for 6080% of the music played on album rock stations. The first station to broadcast the format full time, and the first station to use the term "classic rock" on the air was KRBE-AM (Houston) in 1983. Program director Paul Christy designed the format to play only early album rock, from the 1960s and early 1970s, without any current music or Top 40 material.

Classic rock in recent years has been expanded to include glam metal and progressive rock acts. These artists are often put on "late classic rock" stations (such as XM Classic Rewind) while the more traditional artists are put on "early classic rock" stations (such as XM Classic Vinyl). Even "late classic rock" stations, for the most part, have avoided playing 1990s rock such as early alternative rock and grunge because of the dramatic change in the tone of rock music during that time frame (Music Choice's "Retro Rock" is a notable exception to this). Even though new bands sometimes mimic the classic rock sound (e.g. The Black Crowes), they are not considered a true classic rock band because they are in the wrong era (not early 60s to early 80s). However, classic rock bands from the original era who still produce new music outside of that classic rock era (like The Rolling Stones) are grandfathered in and are still defined as classic rock (as long as their style hasn't changed)