Where to catch Pikachu

In Paldea (Scarlet & Violet)

• Artazon — Walk
• East Province (Area One) — Walk
• South Province (Area Four) — Walk
• South Province (Area Two) — Walk
• West Province (Area Three) — Walk

In Kitakami (Scarlet & Violet – The Teal Mask)

• Apple Hills — Walk
• Kitakami Road — Walk
• Kitakami Wilds — Walk
• Oni Mountain — Walk
• Paradise Barrens — Walk
• Timeless Woods — Walk
• Wistful Fields — Walk

In Hoenn (Ruby, Sapphire & Emerald)

• Hoenn Pokémon Center — Gift
• Safari Zone — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Route 2 — Walk

In Kanto (Red, Blue & Yellow)

• Kanto Power Plant — Walk
• Pallet Town — Gift
• Viridian Forest — Walk

Pikachu — full Pokédex entry