Monitor was an American weekend radio program broadcast live and nationwide on the NBC Radio Network from June 12, 1955, until January 26, 1975. It began originally on Saturday morning at 8am and continued through the weekend until 12 midnight on Sunday. After the first few months, the full weekend broadcast was shortened when the midnight-to-dawn hours were dropped since few NBC stations carried it.

The program offered a magazine-of-the-air mix of news, sports, comedy, variety, music, celebrity interviews and other short segments (along with records, usually of popular middle-of-the-road songs, especially in its later years). Its length and eclectic format were radical departures from the traditional radio programming structure of 30- and 60-minute programs and represented an ambitious attempt to respond to the rise of television as America's major home-entertainment medium.

The show was the brainchild of Sylvester (Pat) Weaver, whose career bridged classic radio and television's infancy and who sought to keep radio alive in a television age. Believing that broadcasting could and should educate as well as entertain, Weaver fashioned a series to do both with some of the best-remembered and best-regarded names in broadcasting, entertainment, journalism, and literature taking part. Monitor and the Sunday-afternoon TV documentary series Wide Wide World were Weaver's last two major contributions to NBC, as he left the network within a year of Monitor's premiere.