AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave bands also. Once AM was the only commercially important method for broadcast signal modulation. Today, it competes with FM broadcasting for mobile reception of music and speech, as well as with various digital modes distributed from terrestrial and satellite transmitters.

AM was the dominant method of broadcasting during the first eighty years of the 20th century and remains widely used into the 21st.

AM radio began with the first, experimental broadcast on Christmas Eve, 1906, by Canadian experimenter Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I. San Francisco, California, radio station KCBS claims to be the direct descendant of KQW, founded by radio experimenter Charles "Doc" Herrold, who made regular weekly broadcasts in San Jose, California, as early as June 1909. On that basis KCBS has claimed to be the world's oldest broadcast station and celebrated its 100th anniversary in the summer of 2009. The great increase in the use of AM radio came late in the following decade as radio experimentation increased worldwide following World War I. The first licensed commercial radio services began on AM in the 1920s. XWA of Montreal, Quebec (later CFCF, now CINW) claims status as the first commercial broadcaster in the world, with regular broadcasts commencing on May 20, 1920. The first licensed American radio station was started by Frank Conrad, KDKA in Pittsburgh, Pennsylvania. Radio programming boomed during the "Golden Age of Radio" (1920s–1950s). Dramas, comedy and all other forms of entertainment were produced, as well as broadcasts of news and music.