Anakin Skywalker was portrayed by Jake Lloyd in "The Phantom Menace".

Hayden Christensen played Anakin Skywalker in "Attack of the Clones" and "Revenge of the Sith". Hayden Christensen donned the armor of Darth Vader in the final scenes of Episode III.

David Prowse was the main actor behind the mask in the original trilogy.

During the lightsaber fight scenes, stunt performer and fencer, Bob Anderson stepped in as Prowse was considered an unskilled swordsman who kept breaking the poles that stood in place of the lightsabers.

Sebastian Shaw was in "Return of the Jedi" when Luke unmasks Anakin in the Death Star.

James Earl Jones provided Vader's voice, but was initially uncredited in Star Wars and The Empire Strikes Back because he felt his contributions were too small to warrant recognition.

More Info: en.wikipedia.org