Where can you catch pikachu in pokemon red?

In Pokémon Red, Pikachu can be caught in the Viridian Forest, which is located just north of Viridian City. To get to the Viridian Forest, leave Viridian City via the north exit and you'll enter the forest. Pikachu can be found in the wild, so make sure to have a Poké Ball ready to catch it.