How old was Mozart when he wrote his first opera?

Explanation

"Apollo et Hyacinthus" is an opera by Wolfgang Amadeus Mozart. It was written and first performed in 1767 in Salzburg, when Mozart was just 11 years old. It is Mozart's first true opera, and was based on Greek mythology. According to legend, Hyacinthus was killed accidentally when he was struck in the head by a discus thrown by Apollo. When he died, Apollo let a hyacinth spring forth from the spilled blood.