Who was the first Jew? I always thought it was Abraham, but in school we learned that it was Ezra.
Judaism is a covenant between G-d and the Jewish people. The details of the covenant were provided in full, by G-d, at Mount Sinai. This took place 3,319 years ago, long before the time of Ezra. Abraham is considered the first Jew because G-d informed him that the covenant would be coming, as it did, through the line of his son Isaac and his grandson Jacob.
Regards, Eliahu Levenson