The celebrated composer Wolfgang Amadeus Mozart was baptized January 28, 1756, the day after his birth, at St. Rupert's Cathedral in Salzburg as Johannes Chrysostomus Wolfgangus Theophilus Mozart. This event, normally decisive for its purpose, was for Mozart only the beginning of a lifetime of fluctuation in what he was called, either by himself or by others.

Mozart's first two baptismal names record that his birthday, 27 January, was the feast day of St. John Chrysostom. "Wolfgangus" was the name of his maternal grandfather and "Theophilus" a name of his godfather, the merchant Joannes Theophilus Pergmayr. Later, his father dropped the Latinate ending of "Wolfgangus" in favour of "Wolfgang," and also dropped "Johannes Chrysostomus."

Mozart often enjoyed making small changes to his name, in particular his middle name "Theophilus", which means "lover of God" in Greek. Only on very rare occasions did he use the now-familiar Latin version of the name, "Amadeus", much preferring the French versions "Amadé" or "Amadè". He was also known to occasionally use the Italian "Amadeo" and the German "Gottlieb".

The use of multiple language versions of the same name was perhaps common for composers in Mozart's day. Joseph Haydn went by "Joseph" (English and French), "Josef" (German), and "Giuseppe" (Italian); and Ludwig van Beethoven likewise published as "Luigi" (Italian) and as "Louis" (French).

On his wedding registry in Vienna's St. Stephen Cathedral, Mozart used the name "Adam". He also sometimes spelled his name backwards.