Magnemite locations — where to catch

In Paldea (Scarlet & Violet)

• East Province (Area One) — Walk
• East Province (Area Three) — Walk
• East Province (Area Two) — Walk

In Blueberry Academy (Scarlet & Violet – The Indigo Disk)

• Canyon Biome — Walk
• Chargestone Cavern — Walk
• Polar Biome — Walk

In Hisui (Legends: Arceus)

• Space-time distortions — Walk

In Sinnoh (Diamond, Pearl & Platinum)

• Fuego Ironworks — Walk
• Route 222 — Walk

In Johto & Kanto (HeartGold & SoulSilver)

• Johto Safari Zone — Walk
• Route 11 — Walk
• Route 38 — Walk
• Route 39 — Walk
• Route 6 — Walk

In Hoenn (Ruby, Sapphire & Emerald)

• New Mauville — Walk

In Kanto (FireRed & LeafGreen)

• Kanto Power Plant — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Route 11 — Walk
• Route 38 — Walk
• Route 39 — Walk
• Route 6 — Walk

In Kanto (Red, Blue & Yellow)

• Kanto Power Plant — Walk
• Route 10 — Walk

Other games (8)

• Brilliant Diamond / Shining Pearl (Gen 8): Fuego Ironworks
• Sword / Shield — The Isle of Armor (Gen 8): Brawlers' Cave, Challenge Beach, Courageous Cavern, Fields of Honor, Forest of Focus, Stepping-Stone Sea
• Let's Go, Pikachu! / Let's Go, Eevee! (Gen 7): Kanto Power Plant
• Ultra Sun / Ultra Moon (Gen 7): Alola Route 1, Hauoli City, Malie City
• Sun / Moon (Gen 7): Alola Route 1, Hauoli City, Malie City, Poke Pelago
• Omega Ruby / Alpha Sapphire (Gen 6): Hoenn Route 110, New Mauville
• Black 2 / White 2 (Gen 5): Virbank Complex
• Black / White (Gen 5): White Forest

Magnemite — full Pokédex entry