Must See TV was an American advertising slogan that was used by NBC to brand its primetime blocks during the 1990s, and most often applied to the network's Thursday night lineup, which featured some of its most popular sitcoms and drama series of the period, allowing the network to dominate prime time ratings on Thursday nights in the 1980s and 1990s. Ratings for NBC's lineup fell during the mid-to-late 2000s. The slogan was retired in 2015 amidst NBC's transition to airing more drama series on Thursday nights. The branding returned for the 2017–18 television season but was removed for a second time in the winter of the 2020–21 television season.

In popular culture, the phrase is most strongly associated with the network's entire Thursday night lineup, including both sitcoms and dramas, which dominated the ratings from the 1980s through the late 1990s.

As originally conceived, "Must See TV" originally applied to sitcoms only (dramas would normally be promoted separately), and for much of the 1990s the phrase was used several nights a week as an attempt at brand extension. At one point in the fall of 1997, the brand was used five nights a week, with four sitcoms a night from Monday to Thursday and two more on Sunday. NBC itself would later adopt the more common interpretation; the 2002 retrospective, 20 Years of Must See TV, focused on NBC's overall dominance on Thursday nights from 1982 onwards, and overlooked extensions such as "Must See TV Tuesday."

By 1979, NBC had fallen to third place in the Nielsen ratings. Network executive Fred Silverman, who previously led ABC and CBS to the top of the ratings, joined the network the year before; however, he could not bring the same ratings success he had as programming whiz at the latter two networks, resulting in a string of new programs that were derided by critics and eventually being canceled after a few showings. The 1980–81 television season was the low point for NBC; as the network had only three shows in the Nielsen top 20; one of them was the sitcom Diff'rent Strokes, starring Gary Coleman and Conrad Bain, with several of its episodes revolving around serious issues such as racism, alcoholism, child abuse and others, which were dramatically explored. Debuting on Fridays and garnering modest ratings, Diff'rent Strokes entered NBC's Thursday night lineup for the 1981–82 season, which, prior to the beginning of the season, Silverman left NBC in the summer of 1981, and was replaced by Brandon Tartikoff, who became a very important key point behind NBC's return to the top.

The 1981 fall season marked the very first time NBC made an attempt to create a two-hour comedy block on Thursday nights comprising the 8–10 p.m. slot, with Diff'rent Strokes being joined by the returning Harper Valley –starring Barbara Eden, formerly from I Dream of Jeannie–, and newcomers Gimme a Break! –which stars Nell Carter as the housekeeper for a widowed police chief (played by Dolph Sweet) and his three daughters– and Lewis & Clark –a starring vehicle for Gabe Kaplan after Welcome Back, Kotter–, all of them being followed by the critical-acclaimed police drama Hill Street Blues. Midway through the 1981–82 season, Harper Valley and Lewis & Clark were removed from NBC's Thursday schedule, and later were canceled, being replaced by Fame, a musical television series based on the 1980 film of the same name.

Branding the quality Thursday night lineup began during the 1982–83 season, which NBC promoted Fame, Hill Street Blues, Taxi (which was renewed by the network after being canceled by ABC after four seasons) and new arrival Cheers, as "America's Best Night of Television on Television". Diff'rent Strokes and Gimme a Break! were moved to Saturdays at the beginning of the season, with Strokes remaining on that night until its cancellation in 1985 (only to be renewed by ABC for an additional season), and Break! returning to Thursdays following the underperformance of Taxi, which at mid-season, was moved to Saturdays, and later to Wednesdays, to be eventually canceled for a second time by NBC. Fame also ended its two-season network run on NBC to be revived the following season in first-run syndication, with a mid-season replacement, Mama's Family –starring Vicki Lawrence– which debuted on Saturdays, moving to Thursdays during the summer, following Fame's removal from NBC's schedule. Meanwhile, Cheers, which starred Ted Danson and Shelley Long (and later, Kirstie Alley), set in the titular bar in Boston, where a group of locals meet to drink, relax, socialize, and escape from their day-to-day issues, despite debuting with critical acclaim, ended its first season with unimpressive ratings, as the fourth-lowest rated show for the 1982–83 season (74th out of 77 in that year's ratings), and was nearly canceled by NBC; however, Cheers was renewed for a second season, in large part due to Tartikoff's continued support to the show, as well as its slowly increase on viewership through its summer reruns, garnering higher ratings than when it first premiered; but also its early success at the Primetime Emmy Awards, receiving for its first season, 13 nominations in 1983, and winning five of them, including a Primetime Emmy Award for Outstanding Comedy Series. Cheers remained as one of NBC's most successful shows on Thursday nights, becoming a top-ten hit starting with its fourth season, and reaching number one during its ninth season, earning 28 Primetime Emmy Awards from a record of 117 nominations.

The 1983–84 season saw none of NBC's fall new shows to be renewed for a second season, and Thursday nights weren't the exception. One of the new shows that season, was the sitcom We Got It Made, starring Teri Copley, which initially started with strong ratings, however, critics and the general public lambasted the show, which eventually damaged its viewership as the season progressed. In December 1983, NBC decided to change its Thursday lineup, in order to make room for soon-to-be hit shows to join Cheers, Gimme a Break! and Hill Street Blues, such as Michael J. Fox's Emmy-winning sitcom Family Ties, which reflected the social shift in the United States from the cultural liberalism of the 1960s and 1970s to the conservatism of the 1980s, which debuted on Wednesdays to modest ratings, but moved to Thursdays midway through its second season, in which ratings began to rise as a result. Another show, Dabney Coleman's Emmy-nominated series Buffalo Bill featured the misadventures of an egotistical talk show host, played by Coleman, and his staff (including Geena Davis and Joanna Cassidy –who won a Golden Globe Award for her role–), which despite having been nominated for eleven Primetime Emmy Awards during its run (including two for Outstanding Comedy Series), Buffalo Bill fared not-so-well on ratings and was canceled by NBC after two abbreviated seasons. All these changes resulted in the moves of We Got It Made and Mama's Family to Saturdays, but both shows were canceled at the end of the 1983–84 season, eventually reviving years later for syndication. In the spring of 1984, Buffalo Bill was replaced by another short-lived comedy The Duck Factory, becoming Jim Carrey's first lead role in a Hollywood production (coincidentally, Carrey previously guest-starred on an episode of Buffalo Bill, prior to the premiere of The Duck Factory). A mid-season replacement for the 1983–84 season, Night Court, set in the night shift of a Manhattan Criminal Court presided over by a young, unorthodox judge, Harold "Harry" T. Stone, played by Harry Anderson, nominated three times as Best Lead Actor in a Comedy Series at the Emmys for his role, and co-starring John Larroquette, who won four consecutive Emmys for Best Supporting Actor in a Comedy Series for his role as Dan Fielding, which aired initially on Wednesdays, was moved to Thursdays during the summer, becoming another staple of NBC's Thursday comedy night in the following years.

What marked the beginning of NBC's dominance on Thursday nights was during the 1984–85 season, when the network premiered a new show to lead that evening: The Cosby Show, which focused on the Huxtables, an upper middle-class Black American family living in New York; the series was based on routines in Bill Cosby's stand-up comedy act, which in turn were based on his family life. The Cosby Show received critical acclaim, with TV Guide listing the series as "TV's biggest hit in the 1980s", adding it "almost single-handedly revived the sitcom genre and NBC's ratings fortunes". The enormous success of Cosby (which earned a Primetime Emmy Award for Outstanding Comedy Series in 1985, and became the highest-rated sitcom and the third-most watched show overall of the 1984–85 season in the US) also helped the other shows on its Thursday lineup increase its ratings dramatically, with Family Ties entering the top-ten for the first time; and both Cheers and Night Court entering the top-twenty; while Hill Street Blues remained steadily on the top-thirty. Prior to the debut of Cosby, CBS was the winner on Thursday nights in the early 1980s, with a powerful lineup consisted of Magnum, P.I., Simon & Simon and Knots Landing, however, that lineup began to lose strength by the mid-1980s, when Cosby debuted, which also marked a major turning point for NBC as well, as the network rose to second place at the end of the 1984–85 season; and reached first place at the end of the 1985–86 season, with Cosby spending five consecutive seasons as the number-one rated show on American television, and tying with CBS' All in the Family, as the only sitcoms in history of the Nielsen ratings as the number-one show for five seasons, earning several accolades, including six Primetime Emmy Awards from 23 nominations.