Radio drama (or audio drama, audio play, radio play, radio theatre, or audio theatre) is a dramatized, purely acoustic performance. With no visual component, radio drama depends on dialogue, music and sound effects to help the listener imagine the characters and story: "It is auditory in the physical dimension but equally powerful as a visual force in the psychological dimension." Radio drama includes plays specifically written for radio, docudrama, dramatized works of fiction, as well as plays originally written for the theatre, including musical theatre, and opera.

Radio drama achieved widespread popularity within a decade of its initial development in the 1920s. By the 1940s, it was a leading international popular entertainment. With the advent of television in the 1950s radio drama began losing its audience. However, it remains popular in much of the world.

Recordings of OTR (old-time radio) survive today in the audio archives of collectors, libraries and museums, as well as several online sites such as Internet Archive.

By the 21st century, radio drama had a minimal presence on terrestrial radio in the United States, with much American radio drama being restricted to rebroadcasts of programmes from previous decades. However, other nations still have thriving traditions of radio drama. In the United Kingdom, for example, the BBC produces and broadcasts hundreds of new radio plays each year on Radio 3, Radio 4, and Radio 4 Extra. Like the US, Australia's network the ABC has abandoned broadcasting drama but in New Zealand on RNZ, continues to promote and broadcast a variety of drama over its airwaves.

Thanks to advances in digital recording and Internet distribution, radio drama experienced a revival around 2010. Podcasting offered the means of inexpensively creating new radio dramas, in addition to the distribution of vintage programs.

The terms audio drama or audio theatre are sometimes used synonymously with radio drama; however, audio drama or audio theatre may not necessarily be intended specifically for broadcast on radio. Audio drama can also be found on CDs, cassette tapes, podcasts, webcasts, or other digital downloads as well as broadcast radio.