In music, Op. 78 stands for Opus number 78. Compositions that have been assigned this number include:
Beethoven – Piano Sonata No. 24 Brahms – Violin Sonata No. 1 Dvořák – Symphonic Variations Fauré – Sicilienne Klebe – Das Rendezvous Saint-Saëns – Symphony No. 3 Schubert – Piano Sonata in G major, D 894 Schumann – 4 duets (soprano and tenor) Tchaikovsky – The Voyevoda