Myfanwy (a woman's name derived from Welsh: annwyl "beloved") [məˈvɑːnʊɨ] (muh-VAHN-ooey) is a popular Welsh song, composed by Joseph Parry and first published in 1875. Parry wrote the music to lyrics written by Richard Davies ("Mynyddog Mwynfawr"; 1833–77). Some sources say it was written with Parry's childhood sweetheart, Myfanwy Llywellyn, in mind, although the lyrics were probably inspired by the 14th-century love-story of Myfanwy Fychan of Castell Dinas Brân, Llangollen and the poet Hywel ab Einion. That story was also the subject of the popular poem, "Myfanwy Fychan" (1858), by John Ceiriog Hughes (1832–87).
The song is still a favourite with Welsh men's choruses. A version has been performed by John Cale, Cerys Matthews on her album of Welsh greats, Tir, and by Bryn Terfel on his album "We'll Keep a Welcome". It is also on O Fortuna, the second album from Rhydian, where he duets with fellow Welsh baritone Bryn Terfel. It is also a bonus track, sung unaccompanied, on the self-titled album by John Owen Jones. The song also is sung in the Welsh language biographical film Hedd Wyn.
The song features in John Ford's How Green Was My Valley and also in the last scene of the Swansea-based movie Twin Town, where it is sung by members of many local choirs, including the Pontarddulais Male Choir.