Home Box Office (HBO) is an American pay television network, which is the flagship property of namesake parent subsidiary Home Box Office, Inc., itself a unit owned by Warner Bros. Discovery. The overall Home Box Office business unit is based at Warner Bros. Discovery's corporate headquarters inside 30 Hudson Yards in Manhattan's West Side district. Programming featured on the network consists primarily of theatrically released motion pictures and original television programs as well as made-for-cable movies, documentaries, occasional comedy and concert specials, and periodic interstitial programs (consisting of short films and making-of documentaries).

HBO is the oldest and longest continuously operating subscription television service in the United States. HBO pioneered modern pay television upon its launch on November 8, 1972: it was the first television service to be directly transmitted and distributed to individual cable television systems, and was the conceptual blueprint for the "premium channel," pay television services sold to subscribers for an extra monthly fee that do not accept traditional advertising and present their programming without editing for objectionable material. It eventually became the first television channel in the world to begin transmitting via satellite—expanding the growing regional pay service, originally available to cable and multipoint distribution service (MDS) providers in the northern Mid-Atlantic and southern New England, into a national television network—in September 1975, and, alongside sister channel Cinemax, was among the first two American pay television services to offer complimentary multiplexed channels in August 1991.

The network operates seven 24-hour, linear multiplex channels as well as a traditional subscription video on demand platform (HBO On Demand) and its content is the centerpiece of HBO Max, an expanded streaming platform operated separately from but sharing management with Home Box Office, Inc., which also includes original programming produced exclusively for the service and content from other Warner Bros. Discovery properties. The HBO linear channels are not presently accessible on HBO Max, but continue to be available to existing subscribers of traditional and virtual pay television providers (including Hulu and YouTube TV, which also sell their HBO add-ons independently of their respective live TV tiers).

As of September 2018, HBO's programming was available to approximately 35.656 million U.S. households that had a subscription to a multichannel television provider (34.939 million of which receive HBO's primary channel at minimum), giving it the largest subscriber total of any American premium channel. (From 2006 to 2018 , this distinction was held by Starz Encore—currently owned by Lionsgate subsidiary Starz Inc.—which, according to February 2015 Nielsen estimates, had 40.54 million pay subscribers vs. the 35.8 million subscribers that HBO had at the time.) In addition to its U.S. subscriber base, HBO distributes its programming content in at least 151 countries worldwide to, as of 2018, an estimated 140 million cumulative subscribers.