In Mauvile city. You can get there by going to the boat after the second gym and giving the letter to Steven. Then the old man gives you the option to go to Saleport City. Go there and do some aqua stuff and go through a route then your there in Mauvile.
that electric type guy
The third gym leader in Pokemon Sapphire is Wattson and he is located in Mauville City.
it is on mauville city
At Mavile city
You get the third badge in sapphire when you get to Mauville. You have to battle Gym Leader Wattson in the Mauville City Gym.
Fight Wally who is by the door
Magnemite,Voltorb,and Magneton.
Ahead North of Mauville, you go to Mt. Chimmney
the third gym leader wattson.
Defeat the 3rd Gym Leader, Wattson, in Mauville City.
In Ruby, Sapphire and Emerald, the 3rd Gym Leader is in Mauville City and in Diamond, Pearl and Platinum, the 3rd Gym Leader is in Veilstone City.
In diamond and pearl, veilstone city in ruby,sapphire and emerald, mauville city