How old was Mozart when he wrote his first composition?

Mozart was a child prodigy. His father—a talented violinist—taught him basic notes on the harpsichord. Mozart composed his first piece of music in 1761 when he was 5 years old; by age 6, he had performed before two imperial courts. In 1763 Mozart and his sister Maria Anna went on tour. For three years the siblings toured western Europe, performing in major cities such as Munich, Augsburg, Paris, and London.

Source: Encyclopedia Britannica