Yeah, if you mean Red, you find him in Mt. Silver, which is to the west of Victory Road. Red will be at the top of the mountain, in the snowy region.
His Pokemon are at high 70s, so be prepared.
Since it is snowing, during the battle, there will be Hail in effect.
l believe he's only accessible when you obtain all sixteen badges and the guard will let you through.
Good luck fighting him!