Hearts of Space is a popular radio show featuring "space" or "ambient" music. It was first broadcast as a late-night San Francisco radio show in 1973 on KPFA in Berkeley and entered syndication on public radio in 1983, quickly growing in popularity. The weekly show focuses each episode on a different theme of ambient or atmospheric music, and starts with an introduction by the host Stephen Hill, the show's founder (who on KPFA called himself "Timotheo"), originally accompanied by coproducer Anna Turner, introducing the theme and the music, followed by almost an hour of uninterrupted music and then some closing words. On KPFA, it was a two hour show, but was shortened for syndication.

The show also spawned a number of projects, including its own record label in 1984 which has released nearly 150 albums, and as of 2001 an online music streaming service. More recently the show can also be heard seven nights a week on XM Satellite Radio.