Myra Hess began to study the piano at the age of five. Two years later, she entered the Guildhall School of Music, where she graduated as winner of the Gold Medal. She studied at the Royal Academy of Music under Tobias Matthay. Her debut came in 1907 when she played Beethoven's Piano Concerto No. 4. She went on to tour through Britain, the Netherlands and France. Upon her American debut she became a prime favourite in the United States, not only as a soloist, but also as a fine ensemble player.
Hess garnered greater fame during World War II when, with all concert halls blacked out at night to avoid being targets of German bombers, she organised what would turn out to be some 1700 lunchtime concerts spanning a period of six years, starting during the London Blitz. The concerts were held at the National Gallery, in Trafalgar Square; Hess herself played in 150 of them. For this contribution to maintaining the morale of the populace of London, King George VI awarded her with the Dame Commander of the British Empire (DBE) in 1941.
In 1946, Arturo Toscanini invited Hess to perform with the NBC Symphony Orchestra in New York City. The 24 November 1946 broadcast concert was preserved on transcription discs and later issued on CD by Naxos Records.
Hess was most renowned for her interpretations of the works of Mozart, Beethoven and Schumann, but had a wide repertoire, ranging from Domenico Scarlatti to contemporary works. She arranged the chorale prelude of "Jesus bleibet meine Freude" (known in English as "Jesu, Joy of Man's Desiring") from Johann Sebastian Bach's Cantata Herz und Mund und Tat und Leben, BWV 147 for piano.
In September 1961, Hess played her final public concert at London's Royal Festival Hall. She was forced to retire after suffering a stroke in early 1961 while in New York on her annual concert tour in America. Although she courageously fought the debilitating effects of the stroke, by the end of the summer of that year it became clear that her public playing days were over. She continued to teach a handful of students, notably Stephen Bishop, during her last years.
On 25 November 1965, Hess died at the age of 75 of a heart attack in her London home. A blue plaque commemorates her at 48 Wildwood Road in Hampstead Garden Suburb.