S4C has reached an agreement with the National Library of Wales-Llyfrgell Genedlaethol Cymru to ensure that all the channel's programmes are protected and transferred to the National Library's care as part of the National Broadcast Archive for Wales.
All S4C content, programmes and series which have been broadcast since the channel's launch in 1982 will be transferred to the Broadcast Archive.
The S4C archive is an important record of Welsh history and a source of information showcasing the development of the Welsh language and broadcasting in Cymru.
Owen Evans, S4C's Chief Executive, said: "We are privileged to hand over our archive to the National Library, to ensure that our programmes and content from the beginning are accessible to all.
"Our archive contains a wealth of history, information and entertainment, and it is vital that this material is available for the nation to study, protect and enjoy. "
The National Library's Chief Executive and Librarian, Pedr ap Llwyd, said: "This is great news that will bring together the broadcasting heritage of Wales, alongside all the other historical sources we have at the National Library."
The project is supported by the National Lottery Heritage Fund.
The National Broadcast Archive project also includes the BBC Wales archive, as well as the ITV Wales archive which was already protected by the National Library.