In music, Op. 20 stands for Opus number 20. Compositions that are assigned this number include:
Barber – Excursions Bartók – Eight Improvisations on Hungarian Peasant Songs Beethoven – Septet Britten – Sinfonia da Requiem Chausson – Symphony in B-flat Chopin – Scherzo No. 1 Dvořák – Moravian Duets Elgar – Serenade for Strings Haydn – String Quartets, Op. 20 Hindemith – Das Nusch-Nuschi Knussen – Where the Wild Things Are Korngold – Das Wunder der Heliane Larsson – Intimate Miniatures (), a suite for string quartet (1938) Matthay – Piano Quartet Mendelssohn – Octet Prokofiev – Scythian Suite Rachmaninoff – Spring Ries – Cello Sonata No. 2 Saint-Saëns - Violin Concerto No. 1 Sarasate – Zigeunerweisen Schoenberg – Herzgewächse Schumann – Humoreske Scriabin – Piano Concerto Shostakovich – Symphony No. 3 Sibelius – , duo for cello and piano (1900) Strauss – Don Juan Tchaikovsky – Swan Lake Wirén – Symphony No. 3 (1944) Zemlinsky – Symphonische Gesänge