Forretress locations — where to catch

In Paldea (Scarlet & Violet)

• Casseroya Lake — Walk
• Socarrat Trail — Walk

Other games (3)

• Omega Ruby / Alpha Sapphire (Gen 6): Route 104, Route 105, Route 125, Route 131, Lilycove City, Mirage Spot Forest, Mirage Spot Mountain
• X / Y (Gen 6): Friend Safari
• Colosseum (Gen 3): Cipher Lab, Shadow Pokemon Lab

Forretress — full Pokédex entry