The final hideout is between Sootopoolis and Mossdeep. Use dive when you see the sub.
north east of lilycove
it is at mt chimney
You don't get it in Sapphire, only Ruby and Emerald
i think you can get one in team magmas hideout in lilycove city but im not sure. good luck;)
There is a master ball in the Team Magma's hideout in Pokémon Ruby Sapphire, and Emerald. Look in the Hoenn region for the Team Magma's base of operations.
go to splatsport city then a guy will be being intervuid follow him and then go back to lilycove CITY
In Pokémon Omega Ruby, you can find a Master Ball in Team Magma's Hideout located in the Fiery Path area. To obtain it, navigate through the hideout until you reach the room with the large, red orb. The Master Ball is located on the ground in a corner of that room. Make sure to explore thoroughly to find it!
Pokemon Ruby in the Cave of Origin after getting your seventh badge. AT THE UNDER WATER CAVE A.K.A.TEAM MAGMAS HIDEOUT
you can get one in team magmas hide out if you have ruby, and one in team aquas hideout if you have saphire. i also heard you can get one if you win a contest twice or more. and if your really lucky, you can get one in the lillycove department store by drawing a lotto ticket.
The master ball is in team magma's hideout near Lilycove city. you have to use dive and complete the area where Groudon is awoken. the masterball is in lilycove go to the department store get a lottery ticket if all the numbers match you will get a masterball
by having strong Pokemon
Team aqua does not own a hideout in ruby, only magma does, however in sapphire it is vice versa, no magma, just aqua.