SOS Encounter: Route 1 (15%), Hau'oli City (15%, Only in Sun & Moon)
Gift: Heahea City (Only in Ultra Sun & Ultra Moon)
Looking for Raichu? It isn't found in the wild in this game — evolve Pikachu (Thunder Stone).
Its base catch rate is 190 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Level Ball, Ultra Ball or Fast Ball.
Evolution: Pichu → Pikachu → Raichu (Thunder Stone).
Pikachu in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)