The Davids

#1 is by Donatello from about 1440.  It is the first unsupported, standing sculpture cast in bronze during the Renaissance.

#2 is by Michelangelo from 1501-1504.  It is the only one of the three depicting David before the fight with Goliath.

#3 is by Verrocchio from 1473-1475.

An essay comparing these three, plus Bernini's David, is found here.