Peter Maag (Ernst Peter Johannes Maag) (10 May 1919 – 16 April 2001) was a Swiss conductor.
He was born on 10 May 1919 in St. Gallen, Switzerland and died on 16 April 2001 in Verona, Italy.
His father, Otto, was a Lutheran minister, and his mother, Nelly, a violinist who performed in the Capet Quartet as second violinist. His great uncles were conductors Emil and Fritz Steinbach. Peter attended the universities of Zürich, Basel, and Geneva. He was mentored by Karl Barth and Emil Brunner in theology, and Karl Jaspers in philosophy. He studied piano and theory with Czesław Marek in Zürich and received further training on piano with Alfred Cortot in Paris. His conducting mentors were Ernest Ansermet, Wilhelm Furtwängler, and Franz von Hoesslin.
He described his association with Wilhelm Furtwängler to be the most important in his life. He performed as pianist in a Furtwängler concert with Beethoven’s Piano Concerto No. 4 in G major. As recounted by Maag, Furtwängler told him: “"Why don't you try to conduct? I have observed you while you were playing the concert tonight, staring at the orchestra more than at the keyboard. It was more you than me that have given the entry”. He followed Furtwängler advice to start out at a small theatre. His new career began as répétiteur and then director at the Swiss Theater Biel-Solothurn from 1943 to 1946. After the first season at Biel-Solothurn, he served as an assistant to Furtwängler prior to the opening of his second season there. After Biel-Solothurn, he became Ernest Ansermet's assistant with the Orchestre de la Suisse Romande.