Irmelin is an opera in three acts with music by Frederick Delius. Composed between 1890 and 1892, it was the first opera which he finished but had to wait until 1953 for its stage premiere. The libretto was by the composer, and weaves together two mythical stories. Philip Heseltine described the opera as a "fairy-tale of quite ordinary kind" and "its form dramatically rather below the level of the conventional operatic text. Though the music was much praised by Grieg and Messager... its performance was never seriously contemplated by the composer". Delius had however assimilated Wagnerian influence in his music, with use of key motifs and a sense of flow through the three acts.