An oggcast is a podcast recorded and distributed exclusively in the Vorbis audio codec with the Ogg container format, and/or other similarly free codecs/formats. For example, a podcast distributed both in the non-free MP3 format and the free Ogg format would not technically meet the definition of an oggcast. In contrast, a podcast distributed in both the Vorbis and Speex codecs would meet the strict definition of an oggcast. The term oggcast is a combination of the word "ogg" from the term Ogg Vorbis, and the syllable "cast", from "broadcast".

The term was coined for the fifth season of the Gnu World Order by Klaatu in 2010, when the show declared itself "the world's first oggcast". At the time, the show was one of the few that released only in free formats, with no MP3 feed as an option. This gave way to other shows using the term, with hosts gathering in the #oggcastplanet connect IRC channel on the Freenode network to compare notes.

The Linux Link Tech Show, one of the longer running Linux podcasts still in production, has a program in the Ogg Vorbis format in its archives from January 7, 2004.

Oggcasters tend to be broadcasters who prefer not to use audio and video codecs that have patent and/or licensing restrictions, such as the MP3 codec.

Recording and distributing podcasts in the Ogg Vorbis audio format has advantages. Mozilla Firefox and Google Chrome web browsers both support playing Vorbis files directly in the browser without requiring plugins. Vorbis may produce better audio quality with a smaller file size than alternative codecs such as AAC or MP3. However, this has not been proven conclusively. Ogg Vorbis is not bound by patents and is considered "free software" in the sense that no corporate entity owns the rights to the format. Some people feel that this is a safer container for their multimedia content for this reason. However, oggcasters can generally not reach as wide of an audience as more traditional podcasters. This is mainly due to the lack of native Ogg Vorbis support in Microsoft's Internet Explorer and Apple's Safari web browser, and the lack of Ogg Vorbis support in many mobile audio devices.

Oggcast Planet maintains a central list of oggcasts.