Karl (Rudolf) Engel (Birsfelden, 1 June 1923 - Chernex, 2 September 2006) was a Swiss pianist.
In 1952 Engel was awarded the second prize at the Queen Elisabeth competition. Throughout his concert career, he cultivated the art song repertory and worked extensively on works of Wolfgang Amadeus Mozart, Ludwig van Beethoven and Robert Schumann. He also held a professorship at Musikhochschule Hannover for three decades.
Engel was a student of Paul Baumgartner (1903–1976) at the Basel Conservatory from 1942 to 1945. After World War II, he studied with Alfred Cortot at the École Normale de Musique de Paris in 1947-1948. In 1952, he won 2nd prize at the Queen Elisabeth of Belgium Competition in Brussels.
Karl Engel toured internationally as a soloist with orchestras, a recitalist and a chamber music performer. He became particularly known for his complete cycles of Mozart piano concertos 1974-1976, Mozarteum Orchestra Salzburg, Leopold Hager (Till Engel & L. Hager playing the two double concertos KV 242 & 365) and sonatas, and the Beethoven Piano Sonatas. His performances of complete piano works of Robert Schumann during the 1970s were highly esteemed. He also distinguished himself as an accompanist, often appearing in Lieder recitals with Dietrich Fischer-Dieskau, Hermann Prey, Peter Schreier and Brigitte Fassbaender. Among his chamber music partners were the cellist Pablo Casals, the violinist Yehudi Menuhin and the Melos Quartet.