In music, Op. 45 stands for Opus number 45. Compositions that are assigned this number include:
Beach – Piano Concerto Berkeley – A Dinner Engagement Brahms – A German Requiem Britten – The Little Sweep Chopin – Prelude No. 25 Fauré – Piano Quartet No. 2 Grieg – Violin Sonata No. 3 Kabalevsky – Piano Sonata No. 2 Liebermann – The Picture of Dorian Gray Madetoja – The Ostrobothnians (), opera in three acts (1924) Mendelssohn – Cello Sonata No. 1 Rachmaninoff – Symphonic Dances Rautavaara – Piano Concerto No. 1 Saint-Saëns – Le Déluge Schumann – Romanzen & Balladen volume I (3 songs) Sibelius – The Dryad (), tone poem for orchestra (1910) Tamberg – Cyrano de Bergerac Tchaikovsky – Capriccio Italien