In the room where the four pokeballs are Electrode Electrode Nugget Master Ball
route 128
team aquas hideout in lilycove
you go to the team aquas hideout near lillycove city
its in team aquas hideout in lilycove, there are 4 pokeballs on the floor. 2 electrodes, a master ball, and something useless.
the master ball is in team aquas hideout. When u find the room with 4 pokeballs the one on the top left (I think) is the master ball.
beat all 8 gyms or in sapphire emerald or ruby you go to team aquas base or you could game shark it
well in emerald ruby and sapphire go to team aquas base solve a puzzle in it and then there will be 4 pokeballs. one is a nuggtet the others are a master ball and two electrode
go to lilycove down by the beach u will find water. use surf and go up a little until u see a cave. go inside and your there!
Capture a pikachu
Fly TO Lilicove city and Surf ontop and you will find a cave,go inside and find the master ball
You can't get another master ball in emerald because there's no one will give you the master ball just the general will give you that.
Team aquas base where they first hide the submarine. It's in one of the rooms
master ball