Karl Reitz (31 January 1887 – 10 February 1943) was a German violist. From 1922 until his death, he was principal violist of the Prussian State Orchestra of the Berlin Royal Court Opera (now Staatskapelle Berlin). He was known as violist in notable string quartets such as the Busch Quartet and the Deman String Quartet, regarded as one of the most renowned chamber music players of his time.