Op. 18

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 ({{lang|sv|En vintersaga}}), 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 {{em|a cappella}} choral songs (1893–1901)
• Strauss – Violin Sonata
• Tchaikovsky – The Tempest
• Zdeněk – The Bride of Messina
• Zemlinsky – Lyric Symphony

{{Opus number disambiguation|Op=018}}