Recieve it from Elm after beating the Elite 4
u buy it for 1000000
have a wank
Team Magma Hideout
You can only get one
In team aqua's hideout
from your enemy teams base
professor elm gives it to you..
You find it in the team aqua hideout.
As you may know, Masterball is the best ball. I have both yellow, silver and gold. After I got the Masterball in either silver or gold, I traded with yellow. By making a pokemon hold the Masterball you trade it and in yellow you can clone it to have more of the best ball in the world. I would guess that Masterball is a lot easier to use when catching Mewtwo that a pokeball.
The professor gives it to you at a certain point
you can only find 1 masterball in any Pokemon game
either from Cyrus or by matching all numbers in the Pokemon lotto