라프 String Quartet no. 5, Op. 138

String Quartet no. 5, Op. 138 in G major is a composition by Joachim Raff, written in 1867. It was first published in 1869 in Leipzig by J. Schuberth & Co. The composer dedicated the quartet to Nikolay Rubinstein. The four movements of the piece last around 31 minutes in a typical performance.