Where do you get rock smash Pokemon FireRed?

You learn Rock Smash in Pokemon FireRed from a man in the south-eastern part of the Pokemon League.

Here's how to get it:

1. Beat the Elite Four and become the Pokemon League Champion.

2. Head to the south-eastern part of the Pokemon League. There's a small house with a man standing outside.

3. Talk to him, and he'll teach you Rock Smash.

Important Note: You'll need to have a Pokemon who knows the move Cut to reach the man who teaches Rock Smash. You learn Cut from a man in Fuschia City after you've obtained the Silph Scope.