The 24-hour news cycle (or 24/7 news cycle) is the 24-hour investigation and reporting of news or informational content, typically by for-profit media agencies engaged in mass communications. The proliferation of mass media and the growth of the cable television market in recent decades has increased competition for audience and advertiser attention, prompting agencies to seek to deliver the latest news in the most compelling manner possible in order to remain ahead of competitors. Television, radio, print, online and mobile app news media all have many suppliers that want to be relevant to their audiences, principally by delivering the news first.

Although all-news radio stations had operated for decades prior, the 24-hour news cycle truly arrived with the advent of cable television channels dedicated exclusively to news in the 1980s. This shift brought about a much faster pace of news production, and an increased demand for continuous reporting with real-time updates. This stood in marked contrast to the slower pacing of the news cycle seen previously in printed dailies. The high premium on immediate coverage would further increase with the advent of online news.

A complete news cycle consists of the media reporting on an event, followed by it reporting on public and organizational reactions to previous reports. The advent of 24-hour cable and satellite television news channels and, in more recent times, of news sources on the World Wide Web (including blogs), has considerably shortened the timeframe within which this process occurs.

The 24-hour news cycle ultimately traces its origins to the dramatic technological changes witnessed amid the Industrial Revolution in the mid-19th century: the development of telegraphic communication systems in 1858—along with improved freight and passenger transport by means of steam and rail travel—allowed rapid communication and travel across long distances and into once deeply isolated communities. These advancements created the earliest shifts in norms surrounding communication, information, and the speed at which the latter was expected and able to be made available to the general viewing public.

Evidently, norm shifts occurred almost instantaneously. Supposedly, the second message ever transmitted by telegraph–immediately following the first sent by Samuel Morse from Washington to Baltimore in 1844–was "have you any news?" In the years that followed, the urgency with which news was received and sought after increased proportionately to improvements in the speed and quality of communications systems.

Ted Turner and Reese Schonfeld pioneered the concept of 24-hour network news with their founding of Cable News Network (CNN) in 1979. First airing in 1980, the network struggled initially, and was widely viewed within the industry as a hopeless enterprise; by the end of the decade, though, it had stabilized, and eventually became a model for other networks as cable television proliferated, competition for viewership among a larger cohort of networks increased, and shifting strategies to sustain viewership substantively and qualitatively changed the nature of media.

Beginning in 1982, following the example set by CNN, C-SPAN extended its broadcast schedule from 8 to 16, then ultimately 24-hour daily coverage; the network states that this extension "enabl[ed] it to add a wider variety of public affairs programming to [sic.] viewers while maintaining its commitment to carry the proceedings of the U.S. House". CNN's success led to the proliferation of round-the-clock cable news stations in the 1990s, seeking to compete with CNNs model.

In 2015, Time magazine noted that the 1995 O. J. Simpson murder case was a significant early example of the 24-hour news cycle.