Magmar locations — where to catch

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

• Coastal Biome — Walk
• Savanna Biome — Walk, Static Encounter
• Torchlit Labyrinth — Walk

In Hisui (Legends: Arceus)

• Firespit Island — Walk
• Space-time distortions — Walk

In Sinnoh (Diamond, Pearl & Platinum)

• Fuego Ironworks — Walk

In Johto & Kanto (HeartGold & SoulSilver)

• Burned Tower — Walk
• Johto Safari Zone — Walk

In Sevii Islands (FireRed & LeafGreen)

• Mt. Ember — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Burned Tower — Walk
• Mt. Silver — Walk
• Mt. Silver Cave — Walk

In Kanto (Red, Blue & Yellow)

• Pokémon Mansion — Walk

Other games (6)

• Sword / Shield — The Isle of Armor (Gen 8): Ballimere Lake, Frostpoint Field, Giant's Bed, Giant's Foot, Max Lair, Old Cemetery, Slippery Slope, Snowslide Slope, Three-Point Pass
• Let's Go, Pikachu! / Let's Go, Eevee! (Gen 7): Pokemon Mansion
• Ultra Sun / Ultra Moon (Gen 7): Wela Volcano Park
• Sun / Moon (Gen 7): Wela Volcano Park
• X / Y (Gen 6): Friend Safari
• XD (Gen 3): Citadark Isle

Magmar — full Pokédex entry