In music, Op. 18 stands for Opus number 18. Compositions that are assigned this number include:
Balakirev – Islamey Beethoven – String Quartets Nos. 1–6, Op. 18 Berlioz – Tristia Brahms – String Sextet No. 1 Britten – Les Illuminations Chopin – Grande valse brillante in E-flat major Finzi – Let Us Garlands Bring Larsson – A Winter's Tale (), a suite for orchestra (1938) Mendelssohn – String Quintet No. 1 Nielsen – Søvnen Oswald – Piano Quintet Rachmaninoff – Piano Concerto No. 2 Ries – Violin Sonata No. 9 Saint-Saëns – Piano Trio No. 1 Schoenberg – Die glückliche Hand Schumann – Arabeske Sibelius – Six Partsongs, collection of choral songs (1893–1901) Strauss – Violin Sonata Tchaikovsky – The Tempest Zdeněk – The Bride of Messina Zemlinsky – Lyric Symphony