"The Woodland Mass" or "The Mass of the Grove" (Welsh: Offeren y Llwyn) is a poem in the form of a cywydd by the 14th-century bard Dafydd ap Gwilym, widely seen as the greatest of the Welsh poets. It is one of his most popular works. Sometimes seen as blasphemous, it presents a woodland scene in which a thrush, sent by the poet's lover, and a nightingale officiate at a Mass celebrating both God and sexual love. "The Woodland Mass" is an example of a common type of medieval Welsh poem in which some bird or beast is used as a llatai or love-messenger, though this poem is unusual in that the message is sent to Dafydd rather than by him.