Modern rock is a term commonly used to describe a rock music format found on American commercial radio. Generally beginning with late 1970s punk but referring especially to rock music since the 1980s, the phrase "modern rock" is used to differentiate the music from "classic rock", which focuses upon music recorded in the 1960s and 1970s. More specifically, the modern rock format consists of commercial radio stations that primarily play alternative rock. As such, the format is also frequently called alternative radio.

A few modern rock radio stations existed during the 1980s, such as WLIR-FM in New York City and WFNX in Boston. Modern rock was solidified as a radio format in 1988 with Billboard's creation of the Modern Rock Tracks chart. The 1988 episode of the VH1 show I Love the '80s discussed INXS, The Cure, Morrissey, Depeche Mode, and Erasure as modern rock artists representative of that year. But it was the breakthrough success of the grunge band Nirvana in 1992 that resulted in a large number of American radio stations switching to the format. Many rock radio stations now refer to their format as modern rock. Modern rock stations primarily play current artists like an active rock station would, but active rock radio stations also mix their current music with classic rock. As alternative rock's popularity in the mainstream declined, heavy metal, nu metal, rap metal, pop punk, emo and other commercially successful forms of rock music also became popular on modern rock radio.

Modern rock is considered by some to be a specific genre of alternative rock. Many fans of alternative and indie rock criticize modern rock as being too homogenized, and merely a poor imitation of the original styles. Still, despite such criticisms, modern rock continues to be one of the dominant forms of rock music on mainstream radio stations.