TG4, formerly known as Teilifís na Gaeilge (TnaG), launched on 31 October 1996, as the third national station in Ireland. TG4 was created with a distinct mission to promote and preserve the Irish language and culture, by making it accessible and relevant to modern audiences and fostering a sense of cultural identity. It operates as a public service broadcaster, offering a wide range of programming entirely in the Irish language (Gaeilge). This focus on Irish language content sets it apart from other mainstream Irish television channels. The most recent available figures have the channel's audience share at 1.96%.

The implementation of Teilifís na Gaeilge (later TG4) was agreed in the programme for government put forward by the Fainna Fail and Labour coalition government (1993 – 1994), which was led by Albert Reynolds. Responsibility for broadcasting was given to the Department of Arts, Culture and the Gaeltacht when TG4 was being established, which was headed by Labour Minister Michael D. Higgins. Michael D. Higgins continued in this role during the tenure of the Rainbow Coalition of Fine Gael, Labour and the Democratic left (1994 – 1997), which oversaw the launch of the channel in 1996.

After being launched by the Irish government in 1996, the channel was for a long time connected to the state broadcaster RTE, although organisationally and editorially independent. However, on 1 April 2007, an independent statutory corporation, Teilifís na Gaeilge was established to manage the channel. Teilifís na Gaeilge is managed by a board, which includes a chairperson (Cathaoirleach) and a director general (Ardstiúrthóir). These positions are currently filled by Anna Ní Ghallachair and Alan Esslemont respectively.
A large part of the station's funding (slightly over €48 million in 2022) still comes in the form of grants from the Irish government, much of which goes towards supporting the creative arts in Ireland. In 2022, TG4 spent €31.1m on creative services in Ireland. Of this €31.1m, €25.608m was spent with independent production companies.

TG4 broadcasts a diverse range of programs, including news, current affairs, drama, documentaries, sports, entertainment, and children's programming, in a mixture of Irish and English, with most Irish-language programming receiving English subtitles. TG4 does not dub live action film or television programming into Irish, although some reality television programming have the English voice over replaced by Irish-language voice over (which is also subtitled in English). TG4 have re-dubbed a number of Hollywood children's films and feature animation into Irish most notably the Harry Potter films. TG4 has also created Cine4 (formally TG4 Film) a film department which invests in Irish-speaking films and mainstream Irish films such as the Oscar nominated Room and An Cailín Ciúin.