Ar hyd y Nos (All through the Night) is a beautiful Welsh folk song and hymn. It has been sung by many famous singers and choirs including Bryn Terfel and Cerys Mathews and even the Australian Olivia Newton John. The song title is also mentioned in Max Boyce's Hymns and Arias! The melody is also used in the hymns "Go My Children With My Blessing” (1983) and “God That Madest Earth and Heaven” (1827).
The tune was first published in 1784 although the composer is unknown. The Welsh lyrics that are most often sung today were written by John Ceiriog Hughes (1832–1887). The most common English lyrics were written by Sir Harold Boulton in 1884 which are not a literal translation.